We had my nieces b-day cake delivered to CRT a couple of years ago. We just called CRO from the resort and asked about a b-day cake for her and they hooked us up. It was great. Give them at least 24 hour notice though. You can alos mention it when making ressies for your resort. we've done this in the past and asked them if it would be possible to have a small cake in the room when we checked in. It was there every time!!!
Also- if you're looking for b-day recognition- mention to CRO when booking your room that you are celebrating a b-day. They will take the info and put it on every ressie you make. Believe me, you'll get b-day recognition!
Don't forget to stop in at the MK and get your b-day button. CM's will be wishing the b-day boy or girl Happy b-day all day long!