I'm not sure your 3 stays are guaranteed as long as all the rooms are in your name. The problem is the 7 night stay and Hilton may look at that stay as the one they credit. As you cannot earn 2 separate stay credits for the same night I could envision Hilton saying only one stay credit. Then you get into a big back and forth with Hilton and there is no guarantee you will win. While it is true the first two stays might post and then you only have trouble getting credit for the third, I had one similar situation where Hilton backed out an earlier posting overlapping short stay and credited the later posting longer overlapping stay. It would be best to have someone else be responsible for that 7 night stay.