When Grandpa sees his three grandchildren loafing around the house-each in their own little world, noses in stuck in a book or eyes focused on a screen-he decides to take action. He suggests they use their imagination and get moving in a game he calls "Giddy up Grandpa!" 

Grandpa's game continues after he falls asleep as he dreams about more and more stupendous kinds of rides.  In the end he and the grandkids discover the surprising answer to the question: What is the most stupendous kind of ride?