As with the rest of the posters, I would like to add my sympathies to your loss and yet how very proud I am you are still going.
Then there is the joy I feel in the fact you were blessed with the man who filled you with so much happiness, because no better gift can be bestowed on us, no matter how short the time.
My cousin died a few months ago, barely into his 30's of a massive heart attack. Wife and 3 kids not knowing where to turn and still, so raw with grief.
A suggestion I gave her and will give to you, is Journal.
Find a beautiful book with pages not of simple paper but equisite design that you can write your thoughts and memories and pour your love into.
You will have him in every step you take at WDW and the legacy he will leave to that grandbaby is now in your hands. Take that book with you and stop to write when the mood strikes. What better way to pay tribute to him, then create a legacy of memories in the place he loved the most?
Write the memories that sights, sounds and smells jog. The silly things that get lost in our memory bank and are yet the first things that wash over us in remembering anyone. You and he had private moments as well as public displays of laughter, joy and profound memories that will never be known unless you write them down.
Let your granddaughter know him through the love of his demeanor, tales he told and be as desriptive as you want. I think so many people feel silly recanting the mundane moments - but when my grandfather died, I gobbled up every letter, every comment people had. I wanted to know everything that made him who he was.
You can create his life and worth for her so she grows up knowing him whether he is physically there to hold her or only through painted memories. They will be as real as his arms that had surrounded her.
I hope this trip gives you peace and a sense of comfort and I thank you for taking the time to remind all of us what is important, even in the midst of your tragedy.