I’m not saying which one of us does which but here’s the scenario, 9 month old and 3 year old in car. You cannot pay at pump (we have one of these which is miles from us).
You’re only paying for fuel, you’re not choosing drink/crisps or anything else, literally in, pay and out.
YABU - you’d take both kids in with you
YANBU - you’d leave them in the car