Can you eat cold foods right after getting braces?

I'm a nanny for a few girls, and the 13-year-old is getting braces tomorrow morning. I was thinking of picking her up a milkshake or a frappuccino from starbucks while she's getting them on as a surprise treat, but I can't remember if you can have cold foods right after getting braces on or if that will hurt or something. Please let me know, thanks! :)