Hi Beth,
The Hoop Dee Doo Musical Revue is one of my all-time favorite things about Walt Disney World. My kids love it. My parents love it. We've seen it seven or eight times. It truly works for everyone.
The Pioneer Hall theater is fairly small. There are not really any bad seats in the house. If you take a look at the
Hoop Dee Doo seating chart, you'll see that all the category three seating is in the balcony, along the sides of the stage. I actually prefer these seats to some of the category two seats that are further back. Even with category three, you'll find that when the performers come into the audience to speak with guests, they'll be up near your seats as well as down on the floor.
In my opinion, if you have a reservation for a date and time that you like, then go ahead and keep it. I don't think a slight change of seating will have much impact on your enjoyment of the show, and a change of plans might impact your enjoyment of the rest of your vacation.
Good luck with your planning and please let us know if you have additional questions.