Hi Jessika, how exciting to be planning a first time visit for your special little princess! Yes, Cinderella's Royal Table is a must, so be sure to book that at 180 days out, if possible, as it is one of the most sought after reservations at Walt Disney World.
My daughter is also six and her favorite park is Magic Kingdom, particularly Fantasyland. So, plan to spend a lot of time there. In addition to the rides and shows there,
Fairytale Hall recently opened for meet and greets with the princesses. I would recommend heading straight for Fantasyland as you enter to get the most out of this area and to insure that you don't miss anything. Then, you could venture to other "lands" in Magic Kingdom.
At Animal Kingdom, my daughter's favorite activity was the
Wilderness Explorers. This program that began this past summer is a great way to see the entire park while learning and "exploring"! She still talks about the interesting things she discovered while doing this interactive activity.
While at Epcot, the
Kidcot Fun Stops are an excellent way to keep the little ones interested in World Showcase. This park is rather large, so these are a great way to add a little break every so often to stop and rest while also doing something fun!
Disney Junior - Live on Stage, Toy Story Mania, Beauty and the Beast - Live on Stage and Voyage of the Little Mermaid were my daughter's favorites at Disney's Hollywood Studios. She wasn't tall enough for some of the extreme rides at this park, so she enjoyed the shows and character meet and greets best here!
Have a great time!
~Allison L