Been there, stilling doing that. I was there in May with 14 mon. DD. She has dairy allergy. My oldest DD did also, but not as severe and outgrew by 1 yr. Anyway, I bought one of those formula holders, they are round and hold three, three scoop portions. I used the soy follow-up formula, Next Step, by Enfamil. My family are not big ice cream eaters, so it wasn't a problem with not eating it in front of her. Basically, everything was the same. We do cheat a little and let her have mac and cheese every now and then. But it really wasn't a problem. We're going back in Dec. and will take our own formula again. But once off the bottle, you can really probably give her all the follow up formula she needs in the room a couple of times a day.
Also, Westsoy makes milk boxes. But they don't have all the vitamins, etc. that kids need. Although, I give regular soy milk sometimes.
Have a great trip.