Honestly, I'm kind of surprised they haven't tried this bolded one yet - I would think they could pretty handily put something like this into Liberty Tree on Party Nights and make a pretty penny. Turn down the lights, do some light redecorating - add The Black Flame Candle, Winifred's Spellbook, some Brooms and a big glowing Cauldron in the lobby, have the sisters making the rounds through the restaurant (would love to see Billy thrown in too, but he might be too intense for an up-close encounter). Add some live entertainment in the form of the Skeleton Band from the movie's Town Hall Party and it would sell out in an instant.
I'm not one for all these upcharge dining parties, but something like this seems like a no-brainer. And as long as the Witches are kept inside there shouldn't be a problem running the Spelltacular at the Castle, I wouldn't think.