"I don't think I can teach them all they need to know."
Let's look at that statement and think about it for a moment. 
Did you teach them to walk, or were you just near-by with your arms reaching out for them?  Skip ahead, did you use quizzes to teach them the characters on Sesame Street or did you just let them pick it up as the show played, pointing out your favorites now and then?  Another jump, did you use flashcards to teach them all the Pokemon creatures or did it seem they were somehow born knowing them?  Are Pokemon part of our genetic code?  I would argue yes, as my children know them ALL by their outline and yet have to pause for a second to remember which of their four grandparents belongs to which of their two parents. 
I think fear of failing your kids is THE number one most common worry of all homeschool parents, whether they unschool, homeschool, school-at-home, use co-ops, bring in tutors, use dual-enrollment and even as they have their kids tested year after year, finding they are average or above across the board.  It's not a bad thing, parents who choose to homeschool are generally the type of people who can think about a thing from more than one angle and who are willing to entertain different possibilities.
Gone are the standardized tests (hopefully) and the feedback from a 'trained professional' to reassure how well or confirm how badly Zane is doing in school.   Parents are taught from pregnancy to rely on doctors to tell them how their child is doing health-wise.  Unborn babies are peeked at and measured and their progress is recorded.  It starts from conception, you compare how you feel with previous pregnancies and to to tales of friends.  Your belly expands and people comment on the size-too big or too small and maybe that's twins in there or it's a girl because you are carrying so high and boys give you more heartburn and so on.  It's never just your own experience, never okay that you are just starving to death and it has to be something salty or spicy or so bland you question if you actually ate something or imagined it.  People ask you what position you conceived in or just speculate on their own out loud while you stand there feeling some inner tug to 'be polite' while they go on and on.
Things you do are 'bad' or 'good' for the baby.  Total strangers will walk up and slap you if you light a cigarette or beam at your bag of broccoli in your buggy.  That's got brain-stuff in it, folic acid, and are you taking your vitamins every day and walking?  Drinking enough water, sleeping on your left side?  Then there is labor-meds or no meds, induction or waiting, home or birthing center or hospital, ob or midwife, and so on and then you have to diaper the thing and dress it and wash it and feed it and all of these things have their own 'right and wrong' advocates right down to a nursing coach to come say, "no, that's not the right way!" as you calmly attach your second child to the breast for the first time, having managed to somehow feed her older brother for a year and half using the same boobs and 'incorrect' technique.  Maybe that was just me, but it all goes to prove my point being: opinions are like...well, you know the saying and it concludes with 'and everybody's got one'.
And that goes to support my other point which is, you are forced into surrender from before birth to do as you are expected and be one of the throng.  This includes handing over your child at the age of 5 to the local school system.  There is comfort in this, it is 'not your fault' if he fails.  Someone will come up with a plan and tell you your part in it if she struggles with a subject, there are medications that enable a child to sit still all day, there are certain expectations and goals that must be met to move ahead in the system and never mind that those are preordained by a group of total strangers who have never seen your child. 
You are set up to not rely on your own gut feelings.  You are told what to think and do, given tasks and their expected outcomes, told dumbed-down versions of historical events as solid fact, shown tired experiments with guaranteed outcomes and told when to begin and end  tasks, how long your report should be, the topic, you are given a list of things to think about, math problems to be solved a single way using one formula and show your work.  Read this in X time, have this in by Friday, the test will cover these particular names and dates.  Use these words in a sentence, spelling counts. 
Any self-expression is ripped out of you first by rote memorization and assigned busy work and then by peers who pick apart what you look like, act like and wear.  School vacations are assigned with advanced reading materials and reports to write, nights and weekends revolve around homework and study.  The whole school year revolves around The Test.  The entire school system revolves around The Score.  You are a cog in a machine and woe if you do not act like a cog.
After getting out of this system, it's no wonder you have no idea what you are capable of.  It is not surprising that you are convinced your child is incapable of learning without being told what to learn and how.  Many homeschool suppliers hand out lists of what your child should know by what age.  Then they show how their boxed curriculum meets these 'requirements' and how your child will learn right on time!  For an extra fee, they have a teacher's guide that writes out exactly what to say to your child and as a free bonus, gives you the answer the child should arrive at! 

The book tells you to say, "Look at the boy in the picture, how do you think he feels?"  (Student should respond "He looks sad.")  "Why do you think he looks sad?"  (Student should respond "He looks sad because his friend is moving away.")" Have you ever felt sad?"  Well duh, it's YOUR kid.  HAS he ever felt sad?  How many conversations have you ever had with ANYONE where you felt the need to chat about how a drawing felt?  What if the 'student' replies 'He looks a bit constipated'?  WHAT are you going to do?  Ack, the book has no back-up plan, it just says, "If student replies incorrectly, correct them."  How can you incorrectly respond to art interpretation?
Put down the boxed curriculum and walk away.  Walk to your car and drive to the library and get a real book. 
It is natural to have some doubt, to worry about how their future will be affected by this choice you have made.  What is not natural is to rely on a textbook written before your child was born that gets updated every so often to tell you what to tell your child about what he sees and thinks.  You have been taught your choices are to be questioned, that unless someone older than you, someone 'smarter' than you can tell you that your choice is correct, then your thoughts or feelings are simply not valid. 
But you CAN do this.  You learn with your child, you will talk to other homeschoolers and the phrase you will hear more than any from the parents is 'This is my education, I am learning every day!'.  They are amazed how easy it is to remember facts and retain information, how much fun it is to research topics and try out experiments.  And they see how their child is just as thirsty for learning as they are, how life and books and travel and movies, conversations, experiences, tall tales and ghost stories, boxes of junk and camping trips all come together to make a world of totally accessable learning, an effortless lifestyle of learning and playing where baking a cake is a lesson in math, reading a map becomes a portal to history, washing your clothes becomes a chance to test stain removers and most importantly-a child who can hypothesize and test their ideas, revise and change their mind, listen and gain some insight and who's opinions are strong, rooted in logic and experience.  A child who does not doubt, one who believes in his own ability to find the information he needs, a child brought up to hear his inner voice.