Soma bay is a nice spot... big lagoon with nice shalow water. At the low tide it can be completly empty but if you use Surfmotion kitecenter you can ride anyway. Staying in Palm Royal hotel is the best option...located directly on kite spot...
In that period we are organising kite trip to Ras Sudr - Egypt (19.9 - 26.9.)... less known and not crowded spot north of Sharm El Sheink, with huge lagoon! We will be staying in the hotel right on the spot... u are very wellcome!
Soma Bay does not get completely empty!
Soma Bay 7 Bft (top of bay) always has water. It has a smaller shallow area, which dries out during summer low tide, but then you have the deep water.
The shallow area next to Surf Motion (former Interconti Hotel, now Palm Royale) dries out on summer low tide, but also has deep water close by.
The main Ras Sudr lagoon is dry on low tide from what I remember (difference during summer or winter?). But I guess the private kite lagoons keep water at any water level.
All locations with pictures on http://locations.splocs.com/kitesurf/country/Egypt.html