Your race experiences and suggestions are why I am doing this. (THANK YOU!) For princess I carried on a pair of running shoes and one sports bra just in case nothing made it. (Luggage made it, it was okay). But I know you have to be prepared for ANY weather. Capris, pants, shirts, sleeves, and tanks. It's over kill but so worth it so that I am ready and not freezing on race morning.
Amazon sells metallic blankets for $8 (10 blankets) and they were great to wear while hanging out in the Wonder Lot. They were dumped as I went into the corral but to have it around me as we walked the 5k to the half start was awesome.
You can learn so many things by reading the threads on here. Lurking in the past year thread I got a lot of great ideas.