Hi Maryann!
I think that doing the Princess Half Marathon with your daughter will be one of the most special days of your lives. I love seeing mother/daughter combinations on the course. The race has a really strong "girl-power" feel, and being with loved ones makes it even more special.
You will definitely not look, nor feel at all out of place on the race course. There is a large percentage of participants in all Disney races that use the run/walk method. (myself included) I think that
Disney trainer, Jeff Galloway, and his run/walk/run method has really opened the door to so many people who have always thought about running, but didn't feel like they could run that far without stopping to walk.
Disney races are truly for everyone. There are all different levels of athletes, and no one will feel out place (or foolish). It's really all about making it to the finish line and having tons of fun along the way!
Definitely sign up with your daughter! It will be an awesome day for you both. Let me know if you have any other questions as you prepare for the race.