People often ask how we manage with three kids and one small car. The answer is: two Radian carseats for the big sisters and a Chicco Keyfit 30 for the baby.
Living in DC, it was really nice having one little car. Then when we decided to have a third kid, everyone told us we'd need a bigger car, so naturally we dug in our heels to prove we did not need a bigger car.
Now that Alexandra is getting longer (and we have experienced our first "mud season"), we may need to rethink our car situation. But not yet. We are going to hang onto our little Versa for as long as we can.