There's a pretty hot discussion about this very subject and the WL on another thread, so let me say first..please don't expect them to do anything special. You can note it on the reservation, but don't be disappointed if they don't do anything.
My suggestion is to inquire at guest services when you check in about the photo. I'm not sure, but I think they have a "supply" of character photos at the WL so it probably wouldn't be a problem getting one. If they indeed have them and you want to be sure your daughter gets a "surprise" photo, you could just slip it in the room yourself.
If it's no big deal one way or the other, just note it on the reservation and see what happens. Please keep in mind though that there are probably dozens of guests who have birthdays every day at the WL alone, so they may or may not do anything.
I have no experience with ordering birthday cakes at WDW, so perhaps another poster can be more helpful as to who you would contact to purchase one.