If you have two cars, you probably have two car seats, or one seat that rides back and forth and is never quite where you need it on a Tuesday morning. Either way, the seat is gear that has to keep working, and it will not tell you when it needs attention. It just sits there while the buckle gets sticky and the strap loosens.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Decide who checks, and how often
Pick one person for each seat and write that name next to the seat in the kids' row of the calendar. A quick look once a month is a reasonable rhythm, and it works best when you attach it to a day you already reset the week. The check takes a few minutes: pull the belt path, tug the harness, press the buckle, and look over the stitching and the straps for fraying.
Read the label before anything else
Most seats have a manufacturing date and an expiration date printed on a sticker, usually on the back or underneath. Find it, take a photo of it, and put the expiration date in the calendar so nobody discovers it in the carpool line. The label tells you when the seat is done, and the manual tells you how the manufacturer wants it cleaned. Keep the manual with the seat, not in a drawer in the other house.
Know what the seat needs after a bump
A small fender-bender in a parking lot still counts. Check the manual for what it says about impacts, and if you are not sure, call the manufacturer or a certified child passenger safety technician before you assume the seat is fine. Many fire stations and local programs offer installation checks, and somebody at the pickup line will know who runs them near you. Looking fine is not the same as being fine.
Decide which seat lives where
If a seat moves between two cars, ask whether it has to. A seat that stays in one car is easier to keep correct than one that gets unbuckled and rebuckled every Thursday. If it must move, make the move a small ritual: the seat goes with the child, the manual goes with the seat, and whoever carries it does the strap check on the way in.
You are not trying to become the perfect keeper of a car seat. You need one person who knows the seat, one place where the expiration date lives, and one habit that catches the loose strap before it becomes the thing everyone remembers. You are already running two houses. The seat should not also be running you.