It all sounds very complicated! It's not a Disney TA, so they don't know the procedure.
What exactly do they need to do, or am I just wasting my time?
Thx
No, if you want it, don't write it off without finding out. Just because it isn't an "official Disney TA" is not to say they won't know what to do. Which one did you book through?
As long as it is not flight inclusive you won't have a problem - or shouldn't. But you CANNOT change the age on a flight inclusive or you won't be allowed through security if your confirmation doesn't match your photo ID exactly and on a package they seem to be unable to amend only part of the booking.
Speak to your TA. Tell the person you are dealing with that you have some food issues with your 8 year old and you know for a fact that as Disney classifies a 10 year old as an adult, you could purchase him a 10 years and up (Disney adult) dining plan to alleviate some mealtime stress for your family. It sometimes helps if you briefly and concisely explain why you want to do this.
Secondly, you need an adult park ticket as the type of park ticket (adult/child) determines the corresponding dining plan category that will be applied.
Explain that you are happy to pay the difference to upgrade the ticket and ask if they could "change" the child's date of birth to reflect him as being 10 at the time of travel.
Assuming you don't require passports or birth certificate for the child for any part of your trip, this should not be a problem. I think your reason is justifiable if it makes your life easier. I had a similar reason, knowing full well that it would be way too much food, but allowing me not to worry about meal times justified the extra cost to me. It sounds like it will make a difference to you too.
You have nothing to lose by trying. Just check afterwards that your request has been carried out. Ask them for an amended invoice reflecting the changes and if it makes you feel better, call Disney or see if you can view your reservation online to double check.
I am sorry I made you worry for nothing.
