Here's the outlook from the 1A world (where I've been for quite a while). The coaches and I both know we HAVE to share kids to be successful. We practice during band time, then for about 2 hours on a Tuesday night for the duration of Marching Season - then THAT'S IT. Everything else is during class time. I make it a point to let my kids know there are NO conflicts between band and athletics (and One Act Play, and UIL Academics) and I even bend when I can for Scouting Activities, FFA contests, etc. As a result - most of the those really talented "want to do everything" kids are in, well, everything. The starting football tailback was my trumpet soloist, our entire Region Champion girls' track team is in band, our recent Tennis Doubles State Runner Up are first chair baritone and flute, and so forth.

I'm super lucky to have a coaching staff that is very supportive of the band, but I also defer to them whenever it seems appropriate.
As an added bonus - since the kids are mostly in athletic practices after school, I usually go home by 4:30 or so (if I'm not driving a bus).

Oh, and we still manage to be successful. Mostly UIL Sweepstakes and 3 consecutive Top 3 SMBC finishes over the past 5 years (including a championship).

Best of luck to you and your program.