Good Luck!!

I would go with a training plan after this race. It just makes you more accountable. I like Hal Higdon because his aren't too ambitious and then for my running style I take a bit of the Jeff Galloway approach. I write down all the mileage amounts on my calendar and that way I know what to expect and push myself for. I never do the carb loading before and haven't had any issues. It really doesn't make sense to me in that it would only benefit you if you ate pasta for breakfast which I won't. I do eat a lot of protein the week before - stuff I know I can digest and that won't upset my stomach. In short, I keep it simple.
Your race won't have water stations and food stations afterwards? I never carry my own water, just my own Gu (since I never like the stuff at Disney especially) and make sure that someone in my party has a big thing of chocolate milk which helps me a lot after all my runs. I take the Gu around mile 9 and alternate between water and powerade (or whatever sports drink) from each water station. I would get bodyglide, some carry it with them so that if they start to chafe, they are set.
I would try to eat some sort of gluten free grain before the race in addition to the banana - but start eating it now in the morning so that you gauge how your stomach handles it. I run my training runs on a nearly empty stomach (only up to five miles) and everything else I eat some sort of grain. The week or two before, I start my pre-race meal which is two apple cinnamon oatmeal packets, and a banana. Be sure to go to the porta potties first before you start. I found for my first half that I didn't gauge the amount of water/powerade that I should consume and went overboard which slowed me down a lot by having to stop at the portapotties. My last half, I never did stop and it was great.
Afterwards, keep moving, keep moving, keep moving...stretch and ice and hopefully you will feel great! Good Luck!!