Each to their own. We don't really have any big petrol stations here, most are small so whichever bowser I park at, I can see the car from the counter inside and if the kids are quiet/asleep, I happily lock the car and leave them in there. If there's a big line-up on a hot day, or they're fussing, I'll take them in (can't leave the a/c on if the keys are taken out), but most of the time it's not busy so I just whip in quickly and pay while keeping one eye on the car to make sure they're okay. I've done this with them since they were newborns, I find it a hell of a lot faster to just lock the car and go in to pay by myself, than to unload one or both squirming kids and try to get them safely into the building You'll know what feels right - some days I leave them, other days I take them in, just go by what feels 'okay' for you. FWIW I've never had anybody even second-glance me when I've left the kids in the car, I'm sure most people understand why I do it even if they choose not to themselves