Sounds like those with pants will likely be wearing jeans or khakis, with either polo shirts or sweaters, and kitsch is acceptable.

Personally I would go just a hair more formal, and go with a dress shirt, vest and a bright red/green themed tie...and lack (or inclusion) of kitsch is a personal choice. You could always put jingle bells on the ends of your garters .

IE wear the jacket & vest, and leave the jacket in the coat check.