S.C.
I remember every team-building exercise being a completely miserable experience when I worked in an office. Mainly because the company was never willing to put any money into it and there's only so much you can do for free. But also because (like you said) participation is mandatory and the activities were always things I never would have done otherwise. We did do bowling once, but it was during work hours otherwise very few people would have shown up. I remember that being fun, but of course you're limited with money.
The only advice I can give you is to make it some kind of competition. I mean, a real competition...not something like Bingo. How about a ping-pong tournament? That's something everyone can play, no matter what they're age or physical ability. You could serve popcorn and sodas to the people watching/waiting for their turn and encourage them to cheer the players on. Just set it up as a elimination thing until it's down to the best two people. Now that's something I could see people getting into. Of course, there's the logistics of locating/borrowing a ping-pong table and getting it into the conference room....but I just come up with the ideas. You make them happen. ;-)