First time we went to Egypt we took pound coins to tip with, dont do it now though, they cant change coins at the bank and they ask you if you will exchange coins for notes, you end up coming home with more coins than when you went.(cant be doing with running round looking for atm's, waste of leisure time im my opinion.
We now use Euro or Sterling, but I found its easier to use Egyptian so you dont have to keep converting to know what your paying.
Word of warning if your going to AI hotels, most hotels bill you at the end of your stay for things like Spa's, drinks you may have to pay for (like Martini, Tia Maria) etc they only accept umblemished notes, (no tears,no writing or marks) and some will only accept a certain amount in cash (think its £200). We usually tip the A La Carte's between £5-£10 depending on how good they are, cleaners we tip at the end of the holiday, and waiters especially the pool waiters, every other day, seems to work we are never short of drinks or service