We celebrated my kids 8th and 13th b-days at Chef Mickey for dinner and it was FANTASTIC! They really recognized them as b-day boy and girl and decorated our table with confetti and place mats they could take home. I ordered a cake when I made my adv. ressie and it was the cutest thing...very detailed with Mickey and Minnie and my kids names. You can get one for less money and no names and it is smaller than the one I got but IMHO don't order one! They will bring you cupcakes with candles(or you can get your own and decorate it!) and by then you don't want any more food anyway. It was really neat but a waste of money on the cake I think! Pluto even helped the kids open some of their presents!
I have a number somewhere that is a birthday/special occasion line (cakes, flowers, balloons, etc.) PM me if you need it.
Get the pin at check in and make sure your child wears it the whole time you are there! YOU WILL get sick of "Happy Birthday ----" but some days you may also get a special treat! My kids got to the front of the line a couple of times, and got lots of pins from CM and we also got our table decorated and a birthday cupcake

at Crystal Palace one morning for breakfast. They also got fairy dust and a pin at DTD on day! Sometimes these things happen for no reason, but with a b-day pin with their name on it, they get to at least "feel" special everyday! On some of the rides(HM, ToT, especially), the kids would forget about the pin and really freak when a CM would have a conversation with them and use their name!
You can't go too overboard, it is Disney after all, but even if you don't do much, it is such a great memory to have just being there!
