I was fortunate to experience Ski Dubai in April and had a wonderful time. I did not need pre-booking.
The website has all the vital information:
http://www.skidxb.com/English/openin...px?mid=1&sid=8
Time of operations: - Beginning of Ramadan until September 13th:
Snow park: 2pm to 1am* / Slope: 10am to 1am*
- September 14th until the end of Ramadan:
Snow park: 10am to 1am* / Slope: 2pm to 1am*
(* Open till 2am on Thursdays and Fridays )
Ski Dubai is attached to the Mall of the Emirates so before or after skiing you can enjoy some shopping or a meal.
Have fun! :-)