Out of the choices you gave, I would personally rather do the party. But I'm not a 10 year old girl.
I realize you're trying to make it a surprise trip so outright asking her opinion is a no go. But with some smarts, maybe you can bring up the subject of character meals and/or the Christmas party and gauge where she's at with them. If you've been to the character meals and/or Christmas party in the past then you can pull up old photos and blame it on you being a 'mom' as a way to kick start the convo. If not, then you could find some videos online from the various vloggers of the Christmas party (and maybe the character meals if you can find them), blame it on falling down a 'youtube rabbit hole', and use that as a jumping off point in to the convo. Then you'll have a better idea of what she would prefer to do.