Thanks for all the suggestions. My 'kids' are in their 20s, so not really kids any more. They are newish divers though. It is tough coordinating with everyone's schedle, so still looking at options. I thought we were going to book in late July, early August to take advantage of the warmer waters, but when we saw that the temp can be 105 to 110 degrees in Cairo and Luxor, we are having second thoughts.
Unfortunatelly, the nicest times for Cairo or Valley of the Kings and diving the Egyptian Red Sea does not coincide. But also be aware that the Egyptian heat is a dry desert heat. Not the sticky, tropical one you'll encounter in Florida or SEA.