Read your contract again...
Mine says developer points can be used within 1 yr from date of contract at any of the three Disneyland Resorts...
I understood that Grand Californian Resort was included in the 3 Disneyland Resorts..I still believe that Developer Points can be used there as long the trip is completed within 1 yr from date of contract..
Good luck with booking..Developer Points are tricky..I am going to try as a first choice to use mine through Interval..I'll monitor how the request is going...I hope I get a "match"...We'll see..At worst worst case scenario, I can always decide to rent the points at SSR if a trade looks unlikely...The developer points must also be used at SSR within 1 yr from date of contract.
Good luck with Developer Points!They're valuable, and no one wants to let them go" by the wayside", that is for sure! Just takes careful pro-active planning and coordination with airfare!