I would vote for the air bed also. The actual aerobeds are very heavy and quite expensive, but if you go to the camping section of wal-mart, they sell twin (and queen) sized basic inflatable mattresses for $10 or so (the queens are about $20). They are pretty comfortable--I have a couple at my house for when extra people stay over. Wal-Mart also sells a compact electric air pump which will blow up the mattress in just a few minutes. I think it is around $15-20. This option would be cheaper than getting another room, and if you bring the stuff back home with you, your kids can use it for sleepovers, etc.
As far as the bathroom goes, having two is great, but you will be able to make one work. When I stayed at the Poly in the 80's, we had five in our room: two parents, two teens, one kid. The kid got his bath the night before. The next morning, parents got up first and got ready, then woke up us teens. Since the sink area is seperate from the shower/toilet, one teen could do hair while the other showered. We also ate breakfast in the room to use up some time while everyone got ready.
I hope this helps.