If you haven't picked out a hotel yet, the Intercontinental and Sheraton Creek are the closest to the main Souk. They are both decent hotels. The really fabulous hotels like the Burj are up the coast in Jumeirah or one or two in the business area on Sheik Zayed road.

Taxis are fine for most things, but I've never heard of anyone taking a taxi into the desert. However your hotel concierge can arrange for a Wadi-bashing tour where a driver takes you up and down the dunes in a 4 wheel drive. That will take up most of a day.