Be warned it's going to be uncomfortably hot. Most expats will be heading in the opposite direction to you, home to the uk for a cooler summer.
Im going to to write as things come into my head so excuse me if it's all a bit disjointed
The best thing for you to do is to get a decent hotel where children's entertainment is provided, most do very good kids clubs which will enable to you have a bit of sun in the safe knowledge dd is having fun and not in the blistering heat.
Dubai mall, the worlds biggest, which is next to the worlds biggest water fountain display, defiantly worth a look, shows start about 6pm every 20 mins. While in the mall check out the largest fish tank and wonder around the worlds largest candy store. There is a aquarium in the mall too. Me dd loves it.
On the top floor of the mall check out www.kidzania.ae/home.php..
Atlantis hotel is worth a visit, they have a brilliant water park and a good children's area, arrive early to get bed and shade. You can go inside the lobby where there is another aquarium type thing. Lots of child friendly dining too.
Most of the malls have children area's where they can play, although i doubt you want a holiday full of soft play day's!
There is a book called 'the entertainer' which is basically a book full of bogof vouchers, use for entry into atlantis and the book pays for itself *260 aed, works out about 48 gbp. Lots of places to eat included in the book too. If you want pm me closer to the time and you can have a few of our vouchers, there is no way we could use them all.
You have to be prepared to get up extra early so its not too hot or go out after sunset. It will still be hot of course but you dont have to worry about dd burning. The malls are open until midnight and its alwayd packed with kids after 8pm!
If i think of more ill come back