Hi there, I can tell you that my husband has researched this extensively, because he doesn't want to pay the crazy rental van fees whenever we travel, which we seem to do a lot of, and we have twin two year olds and a four and a half year old. A rental car can be a fraction of the price of a van - so, that said, it mostly comes down to the car seats, not the car. In Mexico, we managed to squish ourselves (two babies and a three year old at the time) into a Volkswagen something or other hatchback. In Texas we put them all into a Kia Sportage. We have, in the past, bought car seats simply based on the fact that they are narrower than others. Of course safety is first, but narrowness is second in our books! Anyway, you probably don't want to buy a whole set of new seats, though! So, at home we drive a Kia Sedona minivan and don't put all three seats in the back because there is only one car seat anchor in the back of that car - otherwise I'd highly recommend it, though, as it is half the price of a Toyota or Honda and it runs just as well and was actually voted safer than the Sienna for the year we bought it! You could try, though, a Toyota Rav 4, with the extra row of seats, but it looked kind of cramped back there - they are wider than other cars, though. At my parents we drive their Honda CRV and put all three seats in the back of that - not sure if that one has an option of an extra row or not, but it would be worth looking into! Also, I liked that the Honda Odyssey had storage compartments in the floor - how cool is that??! Right now our set up is to have one of the twins in the back next to our four and a half year old, who is in a booster now, and one of the twins' seats in the captain's chair in the middle row - this seems to work best when grandma and grandpa come to visit. It will be great when my mother-in-law comes to visit, too, as she can sit comfortably in the middle row instead of with me or my husband while we're driving (selfish reasoning, I know! Haha). FYI, our Kia Sedona gets great gas mileage, too. So did our Rav 4 when we had one, but ours was just a four-cylinder and that was when we only had one kid. :-) . Oh, and my brother has the Grand Caravan and I also love the way the seats fold into the floor - that would work great for us when we have no visitors!
Good luck and congratulations!