Birthday not on the exact date - sure, as long as you are close to it.
Our DD's birthday is always 2 days before our vacation. So we do not have time for a party (she celebrates either weeks before or weeks after her real birthday) - So on day 1 at WDW, 3 days after her real birthday we celebrate.
She gets a birthday button (has a collection of them now - all the same one). We order a cake for her at dinner. We also order from the WDW florist. See below. So, it's 3 days late - but she has always enjoyed her birthday at WDW and with her friends 3 weeks later
Other ideas- but do cost some $'s
WDW Florist has wonderful gifts - not just flowers, to celebrate birthdays.
You can modify anyhting they have - add balloons, a disney plush, ect.
Check out their web-site &/or call them...
http://www.ftdfloristsonline.com/waltdisneyworldflorist/
1503 Live Oak Ln, Lake Buena Vista, FL 32830
Local: 407-827-3505
Click on 'Our Unique Designs' to find Disney themed items