Hi Peri
Just a few things.......firstly had your daughter definately made prior arrangements to go out to her friends? Has she mentioned to you that she'll rather not stay at home when this family come? Does she think she may not enjoy the night there and why?
She probably will, once they arrive, and "cut the ice" so to speak.
Maybe she's just a little apprehensive about it.....good chat from mum will soon sort that out, my lovely......maybe they can all play together.........cards or a board game etc.
If she really wants to go to her friends, i would just allow her too........would be nice for her to be there when the guests arrive though, if possible, just to say a quick hello to them, but not essential.
Hope you have a great evening, my lovely and dinner's brill......oh and...what time do you want me over?....lol