We just rented a grand caravan and had 2 adults and 1 in a booster and 1 in a car seat. As far as luggage, we had 1 large, 1 medium, 1 large duffle, 1 small roll on, and 2 light weight strollers. If you want everything out of the passenger compartment all of your luggage will not fit. We ended up putting one of the smaller suitcases in the front under the babys feet and the smaller of the 2 strollers. Compared to my Sienna the Grand Caravan doesn't have much room in the back. There is no well and you only have until the top of the 3rd row for safety's sake to store any luggage. It was nice for hauling people (my parents rode with us everywhere when we got to Florida), but for storage space I was disappointed. If you don't mind having suitcases under your feet or sitting next to you on the seat you will be fine. DH is a police officer on the accident reconstruction team so he is pretty fanatical about having things floating around in the luggage compartment.
Maybe I am just spoiled though because I have a Toyota Sienna minivan.