I have a DD15 and DS9 and showed them pictures of it and they are so excited. Then I told them they will get to see tinkerbell and got even more excited.
Don't forget to wear your lime green mickey head!
Not to be a downer, but I would definitely talk "up" the other parts of the party to your kids. The chances are slim that Tinker will not fly, but it does happen. And I would dislike for your kids to be upset and have that ruin the party for them.
We (DH and I) use the following to pump up the kids about the party..
Unlimited sweets and we talk up each of their favorites. DS is a Mango Shooter junkie and DD loves the huge chocolate covered Strawberries.
We make each party a special night for one of the kids. One time it will be a special party for DS's bday, next time DD's bday. (We have been often, if you are going once, name it something special that includes both kids) and really stress that this party is for those reasons. It is quite small compared to other Disney opportunities, that my DS really believed I booked it for him only and only a certain number of people can do this each night.
No waiting 2 hours for the Fireworks... Not sitting on a curb, no tall person 3 seconds before the fireworks start.
FAMILY TIME. Photopass pictures with the castle behind you, and you can hear each other over the table having a conversation.
I am sure you can also find more that fit your family. I know my kids were very disappointed that Tink did not fly the last time we were there, but we made sure to remind them of the other stuff.
Have a GREAT, GREAT time!!!