Mand, I'm not clear on when you bagged school-at-home and began your unschooling journey, but your situation sounds similar to ours.
I pulled ds out of ps when he was 9 (he's 11 now) and we did school-at-home for a few weeks before realizing that wasn't going to work. I worried exactly as you are because ds didn't seem to be interested in anything besides gameboy and legos. Meanwhile, my (then) 6 yr old was gobbling up info as fast as she could. She is the unschooler that you read about in books...teaching herself to read, designing her own science experiments, writing letters to customer service departments and animal rights groups with valid concerns, setting up her own business, etc etc.
I was afraid that ds would never recover from his ps experiences. and would never learn anything at home.
My advice would be, surround yourself with other unschoolers--if not irl, then online. (Try www.unschooling.com
) Also, you might want to try keeping a journal--I was surprised when I did so and found that ds WAS doing more than I thought. He's learned so much about animals--particularly endangered species--through the computer and shows like "The Crocodile Hunter," and magazines. His Lego building slowly grew into an interest in architecture...his tv-watching moved from cartoons to shows like "This Old House" and "Extreme Homes." We discussed different time periods in relation to architecture, differences in building materials depending on climate...one thing led to another, yk? He's worked on a number of home improvement projects in our home and in his grandparent's home. He's designed and built toys and cabinets. He's recently shown an interest in movie-making and has been filming some video--and no, he doesn't know his times tables. ;-) But that's okay, because he knows lots of other things and he's finally, finally, interested and excited about learning again!
Waiting and giving them time is really hard, I know, but I'm convinced it is the right thing to do. Good luck.