Alternate idea:

Dress up as Frozone from The Incredibles, and just tell them you misheard.

Just get a carrot nose, you can be the snowman. His schtick is that he can't wait for Summer, because he doesn't realize he'll melt.

(Yeah, that's a spoiler, but if you haven't seen the movie yet you don't care)

Sven. One of you can be the front and the other the back.

🎶Reindeer are better than people🎶

Go as Elsa, you're going to be the most popular at that party

Put on a beanie with bobble and throw a length of rope over your shoulder and you're kristoff

First read this as an adult costume, through the lenses of a sexy costume.

Dress as one of Elsa and Anna's parents. It's more or less just... 1800's European/Scandinavian fancy dress stuff since other than Sven and the dwarves everyone is of a noble/royal class in classic Disney fantasy style.

You don’t have a lot of options and there’s very few male characters. The culture is like Norwegian/Swedish so dressing like a townsperson wouldn’t be too hard. Here is a character with a pretty typical clothing which would be cool and pretty easy. Another option is just wear all white to dress like a snowman like Olaf.

frozen parties tend to be pretty chill so just don't worry to much how you dress. just let it go.............

Shrek