I have a set of rules for kids and cars.
1. No juice. Water only.
2. Dry snacks if you must. Cheerios vacuum out pretty easily.
That's pretty much it. I recommend potty training to keep the wee off your seats. If you've got a habitual pants wetter you can always take the wife's car.
I have a Bissel SpotBot that does a pretty good job on upholstery.
I have a set of rules also.
#1 no kids
#2 no kids
#3 no kids
;-) LOL