How often do you need to take all 4 anywhere? (I say 4 because you may as well plan for that now. You don't want to sink $1000 into a car if it won't work in 2 years when #4 arrives)
If it's daily, I'd get a van. Getting kids in and out of tiny 3rd row seats blows.
If you ever plan to need to transport all the kids plus a stroller I don't see how it would work.
The other issue is the space in the back row. The comparable vehicle that I have experience with is the Dodge journey. It's rear seat is tiny. The last time my eldest was in it was age 7 and he was cramped. So if you have a baby, 2, 4, and 6, I have a hard time seeing how long that third row will fit the 2 oldest.
Now, maybe this buys you 2-3 years before you buy the van.
The other issue is the type of carseats your kids are in. Depends on ages, but if you've got a baby rear facing and a toddler rear facing (or forward facing with a carseat, not a booster) how is the preschooler going to get into the way back? You can't fold down the middle row due to the carseats. If they have to climb in through the rear hatch, can they buckle themselves?
^^^ that's why I asked how often you drive them. If you're mostly walking around the neighborhood then the climbing and buckling manuevers may be minor. If you're doing it several times a day, it'll probably drive you crazy.