Help! We are trying to find 2 car seats that will fit next to each other in the back of our vectra and insignia. Our rather large 2 year old has out grown his current seat and needs to go into a stage 2/3 with harness and our 4 year old is now big enough to go in one without a harness. The issue we have is finding one of each seat that will fit next to each other as we also have a 12 year old to fit on one of the sides. Anyone been successful in finding ones that fit?