Is it possible and if so how? Recently found out we are expecting dc3 but really can't afford a bigger car, so DCs will be 6,4 and 0. Just now DCs are both in the 9month-4year car seats... So do I have 3 car seats in the back, or does one of them use a car seat in the front? If 3 in the back, then what kind of booster seat would fit between a rear facing and a 9m-4y one (preferably with a back)?