Our first intern wanted to sleep in or be elsewhere on Sunday mornings. Our second intern wanted to sing in church even if she's not religious herself. It's probably tough to really know what you're going to get when it comes to values, especially ones that might affect a family with young kids. Right now it's pretty easy to explain that the intern got home "late" and leave it at that. If our kids were in high school when she came in at 3:30 AM, that might be a little tougher, but as long as they're adults, the interns should be allowed to make some decisions about that. In general, the interns are caring human beings who want to work with kids, so I wouldn't worry too much about values.
The kids get a good lesson in sharing - space, time, food, and transportation. They even get to share their values with the meal-time prayer. Overall, the sharing was a good experience, but one of the factors in not putting ourselves on the list to host next year is Helena's desire to keep her room. We don't have a McMansion, so unless Helena decides to share her space again, we'll have to continue to say no.