I have a 8 year old in one of those boosters without a back, a 4 year old in a 5 point harness front facing booster, and a baby on the way. I have a 2001 Kia Sportage and no we can't afford another car. We need to fit all three seats safely in the back. I was wondering if any of the infant seats are made more slender so we can fit the three back there?