I would recommend Gerbils for many reasons:
1. they are desert animals, so urinate much less than hampsters.
2. if you buy them at the same time you can have 2 (which is much more fun, and not a lot more mess.
3. the are not strictly nocturnal so won't keep everyone awake all night and then sleep all day.
Also, I would recommend an aquarium (as posted above). The plastic habitral type things are pretty at first, but a nightmare to clean and the little guys can chew their way out!!!
I say this after experimenting for years at our daycare with different pets. The gerbils were winners...they were easier care, inexpensive to maintain, played during the day, weren't biters, two were more fun....etc....
If you decide to do this, I'd be happy to give more info about care, I really did my research.
