Wow, a 13th birthday celebration at Walt Disney World sounds so magical. I am so excited for her and you. I have a few suggestions that might make her birthday that much more special.
When I was 13, and still to this day, I loved the water parks at Walt Disney World. Splish splashin' the day away would be a great birthday surprise for your little lady. I suggest checking out Disney's Typhoon Lagoon, which is my favorite of the two. The Typhoon Lagoon Surf Pool features waves that are literally so big, you can actually surf on them. If catching a wave interests her, she can actually take a surf lesson before the water park officially opens for the day. That would be a pretty cool birthday gift! Don't miss out on treating the birthday girl to a Sand Pail! This delightful treat is an actual sand pail filled with chocolate and vanilla soft swirl ice cream topped with waffle cone pieces, cookies, sprinkles, hot fudge, caramel sauce, strawberry sauce and a cherry on top. I think that would be better than a birthday cake any day.
To continue the birthday party after you've had a full fun day at the water park, I'd head over to Splitsville Luxury Lanes at Downtown Disney. What newly 13 year old girl wouldn't love music, bowling and some really great food? Splitsville is such a fun place that she is sure to love. It can be a popular place so be sure to call ahead of time to reserve your lane by calling 407-938-7467.
I hope this gives you a few ideas for your granddaughter's birthday. Happy planning!