Hi Tracy! Congratulations on finishing your half! I also use the run/walk method and love it. I think it has opened the door for many people (like me) who are way too intimidated at the thought of running for 13.1 miles without a break!
They absolutely encourage walkers in all Disney races. I ran/walked the Tinkerbell this January and there were many walkers in the race. Like all runDisney events, the Tinkerbell will require you to maintain a 16 minute/ mile average. As you know from your other event, a brisk walk is more than enough to be above that average.
I think the term "runner" is just used as a generality, but runDisney encourages all runners, walkers, and run/walkers to enter and have a great time at all of their events! In fact, their official trainer,
Jeff Galloway, pioneered the run/walk method that is so successful and widely used with athletes today.
I hope this helps. Please let me know if you have any other questions leading up to the race!