A.M.
Hmmm, this is a tough one. I'm not in your position, so I'm not entirely sure what I would do. I, too, believe that children are taken from the home too soon for "structured" lessons, but if it is necessary........ Anyway, here are the steps that I would take in order to make an informed decision that I would be comfortable with. First, talk this whole thing over with just your husband. Pros/cons/everything--and come up with a list of questions. Do some research on the program itself. If this really is the best thing for him, you don't want to deprive him if it's necessary. Based on some of the concerns that you have listed, see if it is possible to have him go part of the time--whether it be a little each day, only a couple/few full days; what are any and all of your available options where this is concerned? This website is a good way to communicate, but also get in touch with the Head Start program in your area specifically and ask to be put in touch with others already enrolled to get an idea of what it's like and how things are going.
Hope that this gives you a bit of a start. I'd love to know how things work out.