I have no fun food ideas, unfortunately. Very few things are practical to make in a regular-sized English class, and most things are pretty expensive. For my crafts class (16 kids), I just bought some cookies (orange box Chic Choc - not individually wrapped, just cookies in a plastic tray) on sale at HomePlus and poured a little cup of milk for each student. There are Binch cookies on sale right this second which ARE individually wrapped, if that's a big deal to you. Those are about 120W each.
If you have a CostCo membership, I recall seeing mini candy canes on sale the last time I made the trek -- in October.
For fun class activities, I'd suggest doing some simple Christmas vocabulary and then playing a "what's missing" disappearing pictures game (my kids LOVE them), or pin-the-nose-on-Rudolph, or whatever. Making Christmas cards tends to be a huge hit with kids in elementary and middle school. Maybe show a short Christmas video. There are clips up all over the place on the forums. Sing a song like Jingle Bell Rock. (I put up a file with English lyrics, English lyrics rendered in Hangul, and Korean translation in the POP SONGS thread.)
I'm sure someone more creative than I will come along soon. :)
What level do you teach? Elementary, middle school, or high school?