I don't just put them on the belt in the right order - if I can I pack them too
It's one of the advantages of re-usable bags. You can pop them down on the other side of the till and get the check-out people to pass your stuff to you for the correct OCD packing procedure.

And my poor children are already starting to make sure everything is going on in the right order

We could start a support group for fussy grocery packers.