Don't let your disappointment spoil the time they are with you. Yes, they may be being selfish (I couldn't possibly comment) but were you to let it show, it would probably hurry them out of the door. Give it a year or so and the DGDs will be asking "Why can't we stay longer at Granny's/I want to be with Granny/I want Granny to come here/ Granny is more fun etc" This self centredness of the younger generation frequently leaves me speechless but I know that the more I let it rankle, well, the more it hurts me! Enjoy C. Eve and morning then when they have gone - pour yourself a very large glass of champagne, put your feet up, eat the luxury nibbles you have stashed away in the fridge and watch something silly on TV before a luxurious bath and more shampoo in bed! Right now with DH huffing because I have been to see DGSs Nativity and didn't get home until 9.30 and hadn't told him I would be eating at DDs - I would happily leave him to fend for himself and join you, but I'll have forgiven him for being so childish by tomorrow.
Maybe.....