With children that young, I'd say 4 or 5 days. (With teens/preteens, you can just go-go-go and they don't crash - although the adults might!).
My "thing" now that I no longer live down there:
- Disneland Hotel (or one of the other "in the park" hotels) because you just hop on the monorail (it stops at the different hotels that are in park) and go back and forth to the park as often as you like.
- Alternate Park & Swimming... Breakfast in the room / Park for 2-3 Fast Passes (1-2 hours) and however many 'regular' rides can be done in between fast passes (which are 1 per hour) / back to the hotel for a swim & snack / park for 2 fast passes (1 hour) / back to the hotel for lunch and a movie / park for a couple fast passes / hotel for swimming and snack / park / Dinner & Swim / EITHER bedtime or back to the park.
Alternating between the pool and the park keeps us refreshed. When there's a "napper" along, you just trade who stays in the room with the napper during the 1-2 hours back in the park. Most of our food we ate in our room (ask for a fridge) which saved a ton. We do 1 character breakfast (towards the end, so the kids aren't asking for/ expecting it every morning) and 1 park dinner (we like the Blue Bayou in Pirates of the Caribbean, but there's tons of options), and we usually do 1 Disney Food (burgers, etc.) lunch in the park.