old adage:
He who laughs last, laughs best.
recast,
They who laughs last laughs best.
This just doesn't have the same thrust.

Doesn't sound good to me either, but Give everyone their supper sounds just fine. (*That's if we're going by sound and grammar rather than logic.) You don't have to use it if you don't want to, but I find nothing wrong with the usual usage of epicene they. In fact, it fills a hole in English grammar.

Ceci n'est pas un seing.