@Derren Obviously August is the most expensive month, if your 11 year old is not sitting any exams I would take them out of school for just a week personally, that's what I did a few years back.
Anyway Tuesday 29th July 2014 - Tuesday 5th August 2014 Club Siroco All inclusive including 1 x checked in suitcase Total £1273!
Again car hire as above about £76 for the whole week! This was a quick check with Travel Republic but you could try booking flights with Thomson, Ryan Air, Monarch, Thomas Cook, Skyscanner, Easy Jet etc separately and then check out Booking.com or Alpha Rooms for the accomadation to see if doing it separately works out any cheaper, sometimes it does especially if you can find voucher codes for Alpha Rooms.