Hi Jennifer! The Walt Disney World half marathon is really fun! I am sure you will love it!
There are professional photographers spread across the half marathon course. They will take pictures of you as you go by, and then sort them by your bib number so you will have access to seeing your photos and the opportunity to buy them. You will receive the information about the photographers shortly before the race, and it will also be posted on the
Walt Disney World marathon weekend website. There are usually opportunities to pre-purchase all of photos before the race at a discounted rate. I have had good luck with getting great shots this way, and they always get my finish. There will even be a video of you finishing.
However, as much as I love these photos, I also carry either a small camera or at least my phone with a camera during the race. Part of the fun, for me, is capturing the special moments where there may not be a photographer stationed. I always take a picture as I come up on the castle at Magic Kingdom. I also like to take pictures with my favorite characters, and there is no guarantee that a photographer will be around.
So, if you feel like you will want a lot of pictures of the race, other than of just you running, then I would plan to carry something with you. You should do a training run carrying whatever you choose, just to make sure you are comfortable carrying it.
I hope this helps and good luck with your training! Let me know if you have any other questions!