Hi Patricia!
Sometimes the Disney Florist team offers in-room celebrations at various levels according to budget. To get more details, check the Disney Florist site by clicking here.
Or, if you're like me, anywhere I can save a buck is a good deal for me :-)
When in the parks, visit any Guest Relations booth and get a free "Happy Birthday!" pin to wear in the parks. This is an added nice touch as guests and cast members offer "Happy Birthday's" to your son wherever he goes.
If you're staying at a resort, tell them before arrival you're celebrating your son's birthday. Sometimes they'll do a little something special in your room like a balloon or maybe a card.
Also mention his birthday if eating at a sit-down Disney Dining Restaurant. Sometimes they'll do something special like confetti or cupcake with candle.
Of course, this is all at the discretion of the facility, but Disney understands the importance of birthdays, and try to do something just to make his day a little extra special.
May you and family have a wonderful time at Disney!