Ahoy, Karen!
Since you only have one day to enjoy the Walt Disney World theme parks, my answer to your question changes depending on your family. If you have small children traveling with you, then the Magic Kingdom is the place to go. There is nothing like seeing the look on the kids' faces when they see Cinderella's castle for the first time on a WDW trip. My kids still light up when they see it and they are twelve and fifteen! You should not miss classic rides like
Dumbo the Flying Elephant and the Mad Tea Party.
If you have an adult only crew, then you might consider spending the day touring the World Showcase at Epcot. There are lots of places to indulge in an adult beverage, as well as great shows and fun rides. I would book a nice meal at
Le Cellier in Canada - it was delicious on our trip this summer. And, for a treat, try a "cronut" (croissant donut) at the Refreshment Port near Canada...it is seriously delightful!
Does your travel party love thrill rides? Then maybe Hollywood Studios is for you!
Rockin' Roller Coaster starring Aerosmith launches you to 60mph. The Twilight Zone Tower of Terror tells a great story and then drops your elevator car down thirteen stories (we rode this 5 times in one day once!). And, for a bite to eat, nothing beats the 50's Prime Time Café, where the pot roast and mashed potatoes are amazing!
So, you have a tough decision to make. I hope you have a wonderful day in the Walt Disney World parks, followed by the best vacation ever aboard a Disney Cruise Line ship!
Happy Cruising, Tracy V.