I've had quite a bit of experience with small bands. My freshman year in HS, we had 28 - no tubas. It was fun, if mainly because we didn't know any better. By my senior year, we had about 90.
I came back to my HS and taught drums from 2006-2008. We started with 7 in the band, ended with about 25. At a Texas 4-A school. We finished last year with 3 snares, 4 basses and 2 tenors.
Basically, we kept things focused on the trees, rather than the forest. Your director can (and usually will) make life easier by programming music and drill that better suit a small band. Remember to work on the things you *can* control, rather than what you can't.
Have fun - take every opportunity to perform, whether it be rehearsing outside during school hours or a scheduled trip to a middle school. Don't worry so much about what the middle school kids think - get out there and perform. Play the odds - there's bound to be at least *one* kid, no matter what or how well you play - that thinks that's the coolest thing they've ever seen. But they won't know it unless you go play for them!
I'm also the caption head for a 12 member drum corps, and have some experience with that end of it as well. (Of course, we have the advantage of not competing, so we can book gigs more appropriate to our size.)
Heck, one of these days I'd love to play in a *really* big group, just to hear what it'd be like.

Mike