I have done Disney with my son, with my sisters kids and single with friends. Very different experiences, each of them.
Your Granddaughter will love it. 5 is a really great age to go. She will have so much to see and do. But remember, you will feel a lot more tired with her than going without her. Before going with kids I was not as tired. Carrying them, etc., is tiring. Plan on possibly not being able to do as much as you did without her.
If she is a girlie girl, there is the Bibbity Bobbity Bourtique, there are also play times you can have her go to. Tea at GF, cooking classes at GF, Pirates journey and many resorts offer great kids clubs. Pirates and Princess Party would be a great hit and character dining would be great for her, and you too. Chef Mickey's is our fav, there are also Princess meals...one in the castle and one in Norway, I believe. O'Hanas is awesome, too.
I am sure whatever you chooose to do with her, she will have a great time just being in WDW and with her Grandparents. :animwink: