OK, I'm too lazy to go back and quote the poster about the 9-turned-10 DS. Forgive me. But I *think* you may be able to upgrade his admission from child to 10+ at Guest Relations in the theme park. This would involve a fee, but it would only affect him, not your entire family. You may even be able to do this at check-in at your Resort, but I'd be paranoid that the entire package would need to change to 2006 pricing levels for everyone. At a theme park Guest Relations, they may view DS's ticket as an individual entity. Anyone know for sure??? (You may want to post this as its own question elsewhere on this board -- surely someone else has had this experience?)
I can see where you are coming from. You had locked in the prices and just because DS's age changed, it is unfortunate that they want you to pay 2006 prices for the entire family. I hope there is a way to only "upgrade" your 10-yo to the 10+ admission (small cost here, way less than $300) and leave everyone else at the '05 price level. Good luck!