I cant really suggest how much money to take but I do advise you to have several one dollar noteson you for tips etc. I have just come back from sharm and the holiday was spoilt by people asking for money all the time when we were out on trips, the kids being the worst offenders. If you gave them a pound sterling they asked you for 2 and were not impressed with anything less than 20 Egyptan pounds (approx 2quid). People who had been there before had the one dollar notes and one of these seemed to be quite acceptable.
food and drink was not much cheaper than home. oh forgot to say a policeman at the pyramids came up and asked me for money. I must have mug written on my face!
Im sure you will have agreat trip, we did despite the hassle.