I've been in Egypt at Christmas and it was def warm enough to swim (hurghada). Lady year we went to Hilton sharm waterfalls which was good for kids, nice gym, nice massages, lots of pools with a kids' pool and a kids' play area next to the health centre- away from the huge one near the beach and actually quite quiet/relaxing. Not the height of luxury but fun and clean. Have fun, wherever you go.
We want to go to Hurghada or El Gouna in August, yes, I know its HOT but can cope with heat.
Ive got a thread asking for recs for hotels/villa etc.
If you want to go to Luxor, I can recommend an English lady who lives there, she has beautiful flats which she rents out, and will organise food, water, egyptologist to take you places with your own driver. She is amazing!