Departing from PVG is okay since you'll be at Disney, which is only 15 km away, but IC Wonderland is about as far as you can go from PVG and still be in the Shanghai municipality (which is bigger than some of the smaller US states).

The SHA arrival won't just save you time because it is closer, but because it's possible to get from the plane to a taxi in 20 minutes (PVG can take A LOT longer).

HKG-SHA tickets only cost around $150, and sometimes less than $100 close in. You could presumably refund or amend your existing tickets without much of a penalty.