Hello Alison,
Your lil' Princess must be thrilled to be going to Disney World with her favorite Grandparents!
My daughter really enjoyed Epcot as a toddler. Turtle Talk with Crush was one - and is still one - of her favorite shows. Your granddaughter may also like
The Seas with Nemo & Friends,
Journey into Imagination with Figment, and
Living with the Land. And my family loves to experience World Showcase and take in its culture.
I know for some, their toddlers would rather be on attraction, after attraction, after attraction. But for us, a few attractions, mixed in with the sights and sounds of 11 different countries were a perfect fit for our family.
So no, your granddaughter may not be tall enough for Soarin' (although, I could be wrong!), but I think there's plenty at Epcot for her! And don't forget, there are character meet-and-greets there too!
Hope this helps!