In my experience, when the game is in vacation mode and a term at Uni counts the same, then no one ages in any connected world. The Traveler setting for foreign aging shouldn't really be changing that.
I've used lots as minimalist as empty 10x10s with nothing on them but a mailbox to act as staging areas to form temporary households for other purposes and I always keep a couple of those on hand in each world I play. But not for vacations or Uni terms, the Traveler mod option to allow friends in the travel party has always worked fine for me. The place I could see where it wouldn't is if you intend these sims to be strangers or actually dislike each other in which case pre-staging a household would really be the only way unless you want to MC Cheat their relationships up for the trip and then back down again after arrival. But my storyline has never taken me in a direction where I wish to have a bunch of sims who hate or don't know each other suffer through Uni together. :)
I also wouldn't put sims into a temporary holding unit like that if I require sim days to play the other households. It would really be better to keep them all in their original households on hold, as you say, and Add Sim them into the collection lot all around the same time.
