I need help. My DD just turned 4. Is about 41lbs. We want to get a new car seat that is narrower as we will be putting an infant seat in the back and still want a space for a person to buckle. I would prefer to keep her in a 5 point harness for a little while longer before going to a booster with the seat buckle. I also do not want to spend $200. Any recommendations of what worked well???