Musical Chairs

As soon as Hubby and I found out I was pregnant with quadruplets, we knew we would need a larger vehicle. At the time, Hubby drove a Chevy Blazer and I drove a Honda CRV... neither of them is large enough to handle four car seats. We upgraded to a Chevy Suburban, which has been wonderful.
The middle row has a seat which slides forward to access the third row. Hubby took that seat out so we weren't trying to hop over that seat to put infant carriers in the last row. From the moment all the girls came home from the hospital they had "assigned" seats. It wasn't really a plan, but it just worked out that Cakes always sat in the third row on the driver's side. That's the hardest seat to access and she was the smallest and lightest. It made sense that we would lift her infant carrier there so we weren't killing our backs. The next lightest was Tortilla, so she occupied the seat next to Cakes. Roo and Sue Sue always sat in the middle row.
They never questioned this routine... until they could get in the car themselves. We all walk out to the Suburban and suddenly everyone is elbowing each other out of the way to be the first one in the car and the first one to pick her seat. There is no rhyme or reason as to who sits where. Some days everyone wants the back row, other days they all want the middle row. Today Tortilla was angry that Roo and Cakes claimed the third row seats on the way to school. It didn't appease her when I told everyone that Sue Sue and Tortilla will be sitting in the back row on the way home.
I'm trying to come up with a better system, so they know ahead of time who will be sitting where. Although I guess it doesn't really matter what system I come up with... they seem to have a system all their own.