My 15 year old daughter got a postcard a couple of months ago for the moderates - but I wanted a deluxe plus I knew that the postcard name and the ressie name have to be the same -- and you can't make a ressie in the name of someone under the age of 18.
I have always been asked for photo ID when checking in at Disney.
Anyway I called the number told the CM the above - daughter 15 got postcard, we want to go these dates, stay here, what do we do -- it took several calls from him back to marketing with me on hold - but they changed the name in the computer to mine to match up with the PIN number and we were able to use the postcard.
I honestly don't think I would make the reservation in the name of the 5 year old - that could present problems upon check-in
Liz