Congrats on your 1st rD race! You are going to love it; they're so much fun!!
Places to stay ~ it sounds vague, but for the DL races, any of the resort hotels or Good Neighbor hotels around Harbor and Katella are good places to stay. It all depends on how close you want to be to the park entrance, race entrance and how much you want to spend. I always bounce around to wherever the cheapest is. They also have free shuttles for runners and families that weekend from 3-3:30am until 12am.
For eating ~ most people carb up at Wine Country or Boardwalk Pizza and Pasta in DCA, Naples in DTD and there's a Buca di Beppo on Harbor. But there's also tons of places in DTD and across from the parks is Garden Walk which also has a ton of restaurants.
Surviving the run ~ just remember to have fun. It's the 10th for the race and 60th for the parks so it's going to be big. There are character stops in the parks and bands and cheerleaders along the course outside the parks. Also around mile 6.5-7 until we get into the Honda Center parking lot there are people who bring all their old cars it's really neat and a good distraction b/c the middle miles outside of the park until the Stadium are kinda boring. My fave part is as we come off the trail until Angels Stadium and inside the Stadium are a ton of Boys and Girl Scouts cheering for you. It is so awesome. It can be warm so be prepared for that; that's the one downside is that it's California and the weather really can be anything. The 1st year I ran, there was a horrible heat wave, the next couple of years beautiful coastal fog. 2 years ago there was crazy humidity and it was warm, though not as hot as my 1st year.
For costumes, a lot of people make their own getting stuff at Michaels and Joanne's Fabrics. You can look at Halloween websites for costumes as well, just make sure they breath and aren't restrictive. Some people get character shirts in the parks and run in those, some in the race shirt themselves and some just regular running clothes.
There are also 2 other threads set up for the race if you want to join in. They talk about everything from training to travel to costumes. This is the one in the DL part of the forums ~
http://disboards.com/threads/disneyland-half-marathon-weekend-september-4-6-2015-10th-anniversary.3371673/
And this one is in the WISH forum ~
http://www.disboards.com/threads/official-2015-disneyland-half-marathon-thread.3338835/
