Thanks for this. Another question I have is: do I have to be on the plan for the entire duration of my stay at the Disney resort (in my case ASMu)? Reason I ask is we'll spend six days at WDW and then will spend the rest of the trip at Universal and other places so won't be on Disney property. Can't imagine dining plan being used for those days. So can I add a dining plan for 6 of say 11 days at the resort?
The DDP is tied to your length of stay so, no if you don't want to make 2 reservations. You can book a package for 6 days with the plan, make a room only reservation for 5 days (no dining attached), but you may have to change rooms.
You will be paying the adult DDP price for your soon-to-be 10 yr old but can use his entitlements for yourselves, for instance at Signature restaurants.
I'd rather pay OOP and not worry about all of the above