Hi.

I usually do not fight those (obviously this happens maybe two three times a year:0)

And I do understand your situation; children sometimes create those routines maybe being seatted and relaxed just helps their bms.

Anyway, as it is becoming an unoying situation. Perhaps you can ask them to leave them changed. Just facilitate the space and everything needed ready for a diaper change. Ie. globes, wipes, diaper and a bag. Better if it is all close to the sink where they can wash their hands. And a clear set of instructions on how to change diapers.

I have my space always set and ready. So regardless if it is at drop off or pick up (sometimes) parents can easily change and go (everything is facilitated;0)