Westy, I've moved and divided peonies all different times of the year, and haven't killed one yet. I've probably got somewhere around 50 of them. It's best to do it in fall, but if you can't wait, you can do it after they're done blooming. I'd give them a really good soaking the day before the move, don't replant them too deep, and water them in pretty well. You want to make sure you flush out any air pockets around the roots. It's often said that peonies don't like to be moved-it's been my experience that they don't NEED to be divided and messed with for years, but they're pretty good sports about it.
Good luck, and be ready for a workout :)
Brenda