I recently did some thinking about band kids practicing outside of the school day. With athletics, the only time that the kids practice is when coaches tell them to be there and their entire team is practicing. They don't do any work on their own away from the school. At smaller schools, having band practice everyday after school would erase our bands.
You HAVE to build a good relationship with you athletic program if you want your program to grow. That's just fact. It will help you a ton!
As far as region, it's difficult. With the overwhelming amount of apathy with today's youth, they will decide not to do something that they have to work extremely hard to achieve. I give the music to students to work on, but don't push them to audition. Once they get into the music, they can decide. If they practice that music 5 times, then they are better than they were before that. Also, success breeds success. Once you have some kids making the region bands and having a good time with it, that will start to spread among other students.
Athletics is great for a number of reasons, but it's not hard by any means. It takes no talent to give physical effort. Yea you may not be the fastest or make the big play, but every kid can run. So, understanding that has gone a long way for me. What we do is not always difficult, but it is also not ever easy. Plant the seeds for culture and watch it grow!