Cars I can fit car seats in and buckle the seat belts?

We currenlty have a 99 Jeep Cherokee Clic. I have 2 children in car seats one in a no back booster and one in a convertible car seat rear facing, our ongoing problem is that no matter how we arrange the car seats we cannot make it so our oldest (in the booster) can buckle her own seatbelt, and it is hard and time consuming for us as it kinda falls under the other carseat, if we move one to each side the convertible car seat sits too close to the front seat which it isn't supposed too. I watch my niece during the week who is also in a car seat (high back booster) and by the grace of God we have not had to load all 3 kids up yet. We also plan on adding another little one to our family in the future. Any suggestions on what cars I can get to accomidate carseats and buckle the seat belts without "magic" I am looking for alternatives to the mini-van.