It sounds like you have some good ideas. Just don't let it worry you-as several have said-have fun with it. Your idea of laying out where you can is a start. Look for unison passages. Also, most importantly, go very easy on a warm up and try to play as softly as possible during rehearsal. Remember-the typical pit band conductor complaint is trumpets are overpowering the singers. Ease back, way back. Also, you didn't indicate what horn you use or if you have several. Something similar happened to me a year ago aand I carried my 1502 Kanstul (Callichio clone-highly efficient) instead of my Strad. Bet you will do fine.