Boyfriend's Ex-Wife wants to stay with us.?

My live-in boyfriend has two children from a previous marriage. Unfortunately, his kids are in a different country and he hasn't seen them in 7 months. He misses them terribly. His ex-wife agreed to accompany them to the US so that they could stay with us for a week and 1/2 in March. She and her new husband were to stay close by in a hotel while the kids stay with us. Now she's changed her mind and says the hotel is too expensive (even though my boyfriend has very generously offered to SPLIT the cost of the hotel) and is going to have to stay in our apartment. There is no privacy in our apartment as there is an open floorplan. I've never met the kids nor the ex nor the new husband. I'm not sure how to react to this situation. Better yet, I'm not sure how I'm GOING to react after several days together with my boyfriends kids and his ex...all under one roof!! Am I wrong to be extremely concerned?