In general, I typically like to leave this up to a "play to find out" style of resolution. Surely your players can come up with a clever idea!
However, I know that's unsatisfying, so here's a few ways worth considering:
- The most obvious is for the PCs to take the place of the townsfolk. The Merrymakers are really only looking for "entertaining guests" to bring to the wedding. If the PCs prove themselves sufficiently entertaining, whatever that may mean to a fae, then there would be no real need to snag additional townsfolk.
- You could also just straight up wreck the portal. That'd probably piss off the Merrymakers, but the PCs may be able to negotiate their way out of a fight. Or maybe the Merrymakers just scatter at that point to attempt to find another way back into the faerie realm, rather than risk getting stuck.
- The Ringmaster is also supposed to be super hot, so maybe y'all can just fall in love.
- There's also the classic of "burn everything down". Creating a sufficiently large incident would work to frighten the townsfolk away from the carnival and snap them out of the alluring enchantments.