Hi Dominica! I feel your pain! I always wanted to BE a runner, but anything beyond a mile or two was completely overwhelming to me. However, I found out two things. One, running long distances is more about your mental attitude than your physical abilities. If you think you can't, then you will be miserable. And two, I found out about the Jeff Galloway method of running.
Galloway is runDisney's official trainer. He uses a run/walk/run method of running and walking at intervals. You can start at whatever level you want. I started with a 30 second run followed by a 30 second walk and repeated it over and over. I now use a 3/1 ratio, but often play around with the numbers based on how much training I have been doing. It is amazing what having walk breaks can do to your mental well-being. You can also go to www.jeffgalloway.com for more of his information. When you sign up for a runDisney race, you will have access to training plans that are customized for that race. I really can't say enough about his run/walk/run method!
Also, keep in mind that there are thousands of participants in the runDisney events that walk the entire race. It is totally fine too. The rules state that you simply must maintain a 16-minute mile pace. That is a brisk walk. RunDisney really wants their events to be for everybody. They are perfect for elite runners and also for beginners. The course is full of entertainment and volunteers and each race includes running through at least one of the Disney parks.
Definitely check these things out. I know that if I can do it, then you can too! Let me know if you have any other questions about runDisney events! Good luck!