when in the schedule are your classes? that's the biggest question if you're worried at all. If they're at different times in the day there's no problem and i say go for it. If they're back to back or in the same division you'll have to ride one, quickly school the other one, and then show that one. If one of them needs a long school it'll be hard to get it all done in time and you really don't want to rush a green horse during their warm up time. Then again, it's always good to learn how to handle showing multiple horses. What does your trainer say?