Well, I guess it depends on how long you want to spend at the parks, but you certainly could do Disney and Universal in 4 days. You can see everything at Universal in one day and then spend the rest of your time at Disney.
The Sheraton Delfina is in Santa Monica and much too far away from Disneyland. Instad I would recommend staying at one of the numerous hotels in Anaheim. I've heard good things about the
Candy Cane Inn. If you want to go to Universal or most other tourist destinations almost any hotel will be able to help book you onto a tour bus.