I've seen the show done with just a piano and it was wonderful. If you have a great pianist and two powerful singer/actors, the show will be fine. The orchestrations are gorgeous, but not necessary for the story being told. There is a lot of underscoring an damping due to dialogue, so the cast recording is a bit misleading about the difficulty of keeping the orchestra and actors together. I would say if you have limited funds and can't get donations, jut gets. Great pianist (and they have to be great to play Jason Robert Brown) and two great performers, it would be a great show, and most people won't miss the orchestra.
"Sticks and stones, sister. Here, have a Valium." - Patti LuPone, a Memoir