OP back again, thanks for the additional responses.
The younger kids aren't very young--they will be 12, 14, and 16 this summer. The 16 year old could stay by himself, and probably even the 14 year old with him...it's the 12 year old I'm worried about.
I'm thinking you all are right about it not needing to be a 2 night event also. I like what 22:31 said "I'd probably go up the night before, have a nice dinner with your college student, move her in, maybe get lunch together, then head home. " and that is probably what we will do
Thanks again everyone, for the perspective!