We LOVE our Toyota Sienna! I have two kids, age 5 and 3. At one point I had both our Bob Revolution Duallie and our single Bob Revolution stroller in the cargo space of the van. It was a tight squeeze for both strollers, but they did fit. We have the 7 seater, but you can get the 8 seater that has a removable middle seat.
I love everything about the van. Easy in and out for both my kids,5 seats with tether and latch systems for the carseats, of course the top safety ratings on consumerreports.org for the braking system is a must. On many occasions I have had 5 carseats/booster seats, two adults, and all our beach gear in it comfortably. The grandparents enjoy the ride from the third row seat. My Dad gets motion sickness and riding in the third row doesn't bother him at all. We just have the basic LE model with one automatic sliding door (the other is a manual sliding door). We also pack up the kids and all our stuff for a 2 week drive trip from San Diego to S. Dakota every year. Plenty of room for us all to be comfy on the long drive and since we have several food allergies we have to pack a lot of food to go with us on top of the normal luggage and gear. It all fits perfectly with room to spare.
Just be sure to get one with the roof rack and trailer hitch already installed. I didn't realize that we didn't have a trailer hitch on ours and so I will have to get one installed (about $200) so we can bring our kids bikes on our trip to S. Dakota in Aug.
On a side note: My family comes from Hawaii. The kids and I just got back from a week in Hawaii for a funeral. While there we borrowed my uncles Honday Odyssey. No complaints about that van either, except his van didn't have the latch system for the carseats (an older version).
Also what we did before we bought our Toyota was to take all the carseats, strollers, and other stuff that would normally be in the car down to the dealership and we loaded everything into a Siena to see how easy or difficult it would be and to see if everything fit. I had the two carseats installed, and everything in the van in 15 minutes. Then we put both kids in the car and did the test drive. Kids loved the van (we had a Toyota Camry before so they really liked the higher view that they get in the van and more foot space).