Realize that even if you mention it on your ressies and at check in they may do nothing special. They are under no obilgation unless you pay for something special, like a birthday cake, and even then the only thing they have to do is bring the cake.
I believe that at the new dinner there is a wishing ceremony for special occations with the Fairy Godmother and the mice, not an individual ceremony, but one for all of the special occations in the restuarant. And there are no princesses for dinner, so they won't be able to "make a big deal" about anything like they might at breakfast or lunch.
I'm sorry to be so negitive I just don't want you to go expecting lots of magic and be really disappointed if you don't get it. They may very well do things like bring a card and decorate the table, but they might not. I wish that all Disney restuarants would offer a "party package" that could be reserved and paid for so people wouldn't get dissappointed