Since I don't live in so cal, I don't really know about the special ticket deals (like certain tickets from Costco). But I don't think
Disneyland itself sells any special *ticket* deals to residents...
If they are going to use
DVC only for Disneyland Resort, and if they'll be going more than once a year, they will indeed want to look into APs.
Here is the link to the AP info page. Scroll down, and you can click to see the calendar of blockout dates throughout the next 12 months for the 3 APs with blockout dates.
The nice thing is that they can upgrade to a different level whenever they want. If they suddenly find themselves wanting to go to DLR during a blockout period of the AP they have, they can move up a "level". (or if it's just a day or so, they can buy blockout passes for $50 per person per day) The price is NOT pro-rated and the expiration date won't change, but they can upgrade during the year if they need/want to.
But remember, the AP only governs getting into the parks. The resort stay has nothing to do with it.