Just posted this to a coworker, figured I'd post here as well.
We have three as well. Here is our car setup:
Honda Accord Sedan - 2006
Evenflo (always hated that seat - claimed up-to 56 lbs, but our 33lb 2 year olds are getting too tall for it)
Radian (fantastic car seat. I wish we got these earlier instead of the Evenflo)
Honda Odyssey 2009 EXL (includes middle-row center "jump seat" with legal & functional seatbelt for car-seat install)
Graco Nautilus (surprisingly happy with that seat, accomodates our large kids well, inexpensive)
Britax Marathon (great, but does not age well. clips don't work well after any food gets in them. cover loose after just 18mo)
FYI: I was very reluctant to go the minivan route, but we're extremely happy that we did. When you have three kids, looking cool becomes much less important than convenience. Getting them all in and out of the Odyssey is much easier than the car, and from what we've seen better than SUVs as well. The power doors with remote control are a great feature helping onboard the kids after a stop and instantly cooling down a hot car. The massive trunk has even helped on runs to the Home Depot and Goodwill.