My DD will be 6 next week. I am homeschooling her at a Kindergarten level right now.
My mom started doing Bob books w/ her a long time ago...but she (my DD) is really not too keen on learning. And she is happy to make that known.
So I am now really cracking down on her.
We have been working on phonics a lot.
Going over the different sounds and blends.
I also bought this book: http://www.amazon.com/Teach-Your-Child-Read-Lessons/dp/06...
We have been working at it pretty hard for 2 weeks and she is doing great!
Your son is young-he was 3! last week. Personally, if he is showing resistance, I would lay off.
Too much, too soon could backfire. But like T.J. said every child is different...
Hope this helps a little! :)