Depends on where you are going and what you intend doing eg are you in an all-inclusive resort or travelling around? Are you paying for children or is it just you? Are you going to try diving, camel-riding etc?
Food has become dearer (not in western terms) during the last year, but when I was there a couple of years ago a good solid meal was about a fiver. If you aren't a heavy drinker, aren't going snorkelling and are just staying around one place, I'd guess �20 a day would be more than adequate.