Hi Julia,
Wow, you have so much to celebrate! Your trip to Walt Disney World is sure to be special.
My first suggestion is that you get birthday and "I'm celebrating" buttons for your family. When you wear a birthday button, it is magical to walk around and hear cast members and other guests wishing you a happy birthday. Birthday and celebration buttons are available for no additional cost at Guest Relations at any of the theme parks. When you wear a birthday button, you may experience little surprises throughout the day. My daughter was thrilled to receive an extra special birthday cupcake on her seventh birthday at the Plaza Restaurant at Magic Kingdom. It can happen for adults, too. One year my husband wore a birthday button and was surprised with a scrumptious cupcake at the BoardWalk Bakery! You should never expect special treatment because of the birthday button, and then any little surprise that comes up is even more magical. In the same way, when you have reservations for dining, be sure to note on the reservation that you are celebrating birthdays. Again, don't expect anything special and then anything special that happens is extra wonderful!
Disney Floral and Gifts can create amazing gift packages. They have many pre-designed options, or you can work with them to personalize a gift for your son by calling them at 407-WDW-GIFT (407-939-4438). On my daughter's seventh birthday, we had a Minnie Mouse plush holding a bunch of balloons delivered to our room. Another idea is to have a special cake made for your son's birthday by calling the cake hotline at 407-827-2253. Go to disneyfoodblog.com and search "cake" for information on how this works.
However you decide to celebrate, I'm sure that you'll have a great vacation, Julia. Please do not hesitate to ask if you have any further questions!