I'd say convert them to workers, but don't resettle right off the bat. Most cities seem to get up to the size supportable by their city improvements fairly fast in the late Ancient era. In the early, your usually busy founding new cities anyway.
Those workers can easily be used to jump straight to size 10-11 once you get the aqueducts/improvements in place to handle the excess size. Basically, you get your size 12 cities population instantly, you just put half in temporary storage until you are ready for it.
Or you could just pop-rush the excess away.