Thanks for the advice.
I paid $25.00 for the van. I called other placed but got a bad feeling even though they were a little cheaper. The lowest was $18.00, but they couldn't guarantee a van, and would have sent two cars and I would have paid for both. We need to be picked up at 3:45am so I really need someone who I can count on not being late.
I will have 2 -3 luggage pieces, and the kids will carry their carry-ons. It is 5 of us, so I will tip $7.00 and $3.00 for the bags, so an even $10.00. Still feels low to me and if he/she is very nice, I might add a little bit more, but I do feel comfortable with the $10.00. Thanks everyone.