Hi Lori,
The free admission on your birthday promotion was one of the most popular ever at Walt Disney World. And, yes, it was a one-year deal that only applied from January 1 to December 31, 2009.
You are correct that you can get a free birthday recognition button for your son to wear throughout his visit. While special gifts or surprises aren't guaranteed, I've often found that cast members will bring a free dessert or other token to the birthday boy or girl. Be sure to mention when you are seated that your son is celebrating his birthday.
If you are looking for economical birthday treats, consider a set of birthday mouse ears or a hat designed to look like a birthday cake. Speaking of cakes, you can order a 6-inch vanilla or chocolate cake (currently $21) at any table service restaurant except Victoria & Albert's. Just let your server know when you are seated.
Or you can order a custom cake in advance from Disney bakers to be delivered to you. The cake hotline is (407) 827-2253.
Details about those and other celebration options are available at the
Customize Your Celebration website.
I hope that helps. Please let me know if I can answer other questions for you before your visit.
Wishing your son the best birthday ever!
Wilma