A big +1 for the fast pass deals.

We stayed at the Disneyland Hotel when we went. It was worth it to me, just for the convenience. You might consider a cheap stroller (at the park or buy one at Target when you get there) for the 4yo.. lots of walking at that age makes for a cranky kid.

The evenings are generally slower and less packed.

Bring lots of cash, patience, and get ready to have some fun.

(I actually liked California Adventure more than Disneyland)