Well, I have bathrooms (I never got to design them, darn it) and have raised kids in this house, so I might be a little qualified to answer. What has worked is having shower curtains instead of glass on the tub/shower combo, since the shower curtains are easily thrown in the wash or replaced. We have 2 kids per bathroom, but I would trade the 2nd sink in each one for more drawer/counter space. I would not install 2 sinks in a kids' bath.

Tile should go up to the ceiling, and since our kids grew tall, I wish the shower heads were taller. In fact, if I designed them now, I'd put in solid surface showers and only have one tub. We certainly never needed all the tubs. One tub for the whole house would've been enough.

I'd have given the countertops 1 1/2" overhang to prevent drips from going down the cabinet faces. Yeah, that's important. If I think of anything else, I'll let you know.

I agree with Mrs. S. on everything. I would also add a hand held in the tub combo. Hooks instead of towel bars. You have a better chance of a kid hanging a towel on a hook than the bar. Lots of shelves in the showers to hold the many different half used shampoos, conditioners, and soaps especially if one will grow into a teenage girl.

Train your children to hang up towels, don't overflow the bathtub nightly, and treat YOUR house with respect.