Hi Lucy,
Walt Disney World is a fantastic place to celebrate a birthday!
Tarzan is typically not easy to find and I haven't seen him in the theme parks during any recent visits apart from during Mickey's Not-So-Scary Halloween Party last year where he was available for meet and greet along with Jane and Terk. Your best bet will definitely be at
Disney's Animal Kingdom. I would recommend that you stop by at Guest
Relations when you arrive at this theme park and speak to a Cast Member. They will be able to call the Character Hotline to see if
& where he'll be appearing during that particular day. If he isn't, there is a good chance that Terk will be -we have seen her many times here during recent trips.
I do however have some other suggestions to make your sons special day more magical:-
1/ Make a dining reservation for a Character Meal and pre-order a custom cake to be brought to your table during the meal.
2/ Arrange an In-Room celebration or Mickey's Birthday Surprise through Disney Floral & Gifts.
3/Arrange for a gift to be waiting for the birthday boy upon your
arrival at your Disney Resort hotel through Disney Floral & Gifts.
4/ Create your very own Birthday Ear Hat at the Chapeau in the Magic Kingdom theme park.
You will find lots of other ideas on the Customize Your Special Occasion page of the Walt Disney World website
HERE.
I would also be sure to pick up a complimentary birthday button when you
check-in at your Disney Resort hotel or from Guest Relations as you
enter one of the Disney Parks for him to wear throughout your stay. You
will be surprised at just how many Cast Members and other Guests will
stop to wish him a Happy Birthday.
I hope that this has given you some ideas and wish you a magical trip!