I'm assuming you will be competing in Kiwanis with several other schools?
Anyway, your best bet is to practice tonight with a metronome and make sure you are 100% confident with the tempo and the dynamics!
Remember, tempo and dynamics...
Try your best to tune the guy beside you out and listen to the rest of the ensemble
Your eyes should be ALWAYS on the conductor!
If you watch, then you won't get off beat.
Use an earplug in the ear closest to him.
You can use headphones! Or something that prevents you from listening to him, otherwise it will be very difficult to start playing in rhythm.