I have been lurking on your PTR but saw today's post so thought I would pop in. I am by no means an expert runner but I have done a handfull of distance races (10Ks, 10milers, a half). SO take my advice with a grain of salt
I agree with the PP, if you know you will need to walk, the best thing to do is train with scheduled walk breaks. And like PP said, don't wait till you need them because generally, by then it's too late!! Have you ever heard of Jeff Galloway? He advocates walking in distance events and has a lot of info and training programs available, google him!!
Another thing, I sincerely think you goal for these races you have planned is to finish smiling. Don't worry about your time, no matter waht they will all be PRs (personal records) since you never ran those distances before. So don't put any crazy expectations on yourself, just go and have fun!!
Another point, practice fueling. One your runs now you won't need extra fuel but once you get to longer distances, you will. My personal favorite is sport beans, easy to eat on teh run and they taste good! But generally, any run over an hour and you will need to replenish.
Best of the best to you. If you have any other questions feel free to PM me
