Mike,
The first thing I would say is that it is a good thing you are getting out of there!
I went last year and we had to jump through some hoops to get this counted as professional leave instead of personal leave. Things we brought up were the fact that our Robotics team made it to a national competition and the sponsors of that team were allowed to go. The SR. national event is not a KSHSAA sponsored event, but neither is any other national competition such as the Robotics or the Journalism stuff our Journalism teacher takes kids to.
We also have coaches that go to Basketball clinics in Vegas and get that approved. If your coaches do anything like that, it is another way to approach it since there are technique/coach clinics there (last year was J Robinson). That is another way to approach it.
Basically I would look for any precedents that the administration has already set, and ask them to apply the same standard to you.
Good luck!
Kale