Do you absolutely HAVE to go to contest? Do you have the option of going as a non-varsity and playing off the grade I list (still would be a huge challenge with the band you describe)?
I believe I would not go if that were an option. Really work to develop the kids (particularly the ones you say do not play at all). There are some flexband things that could work. Try to find a Spring Contest perhaps where you could get some tangible success without exposing yourself to the criticism of UIL>