When I travel in China, I do not take large amounts of cash with me.  I do have an account with a local bank, and do have a debit card from them.  So, I draw money out as I need it, and if pickpockets get to me, the lost is minimal.

I always make my hotel reservations thru Agoda, booking them in advance, I save from 20 to 50% of normal prices, and pay with my credit card, so less cash needed during the trip.  Hotels in Shanghai (and all over China) will largely depend on luxury and cost (not level of service provided)  for their star rating.  I have stayed at 239 Rmb per night hotels, clean and sufficient for one or two nights of sleep, and I have also stayed at ones above 1,000 Rmb per night for a room just to see how some can live here.  It will be your choice.

Clubbing is the same, probably will depend on how much you drink, what do you drink, and who you drink with.

Besides that, consider taxis, restaurant meals, and other incidentals.  Probably around 3,000 Rmb will do you on a budget minded trip, maybe as much as 5,000 to 10,000 Rmb if you plan to blow Shanghai wide open

It depends on the type of person you are.  I know people that would blow 15,000-20,000 on a weekend in SH.  I'm on the opposite end of that spectrum.  Taking the bus, eating from the small local places, pregaming before the club, then spending the night in a cheap massage parlor or internet bar.... I can enjoy a weekend trip to Shanghai for under 500 rmb (including transportation to get there).