Thanks for the comments on the post below; it seems the majority votes for the "lucky" red race shorts, so I'll probably go with those. As per the questions about temp and the necessity of the shirt: The weather forecast for Sunday morning in DC calls for a low of 56 and a high of 75. To me, that is absolutely perfect running temps. Granted, the race doesn't start until 8 am, so it will be getting warm as we start, but to me, that will still be significantly cooler than here in FL.
Thus, my plan with a shirt is flexible. If it feels chilly to me that morning, I'll start with the shirt on, and if I get warm, I can always shed it and run in just my sports bra. Also, I will be on the lookout at the expo for something that may be more suitable based on my perception of the conditions once I arrive in DC, so who knows? I may find a shell top or a singlet that's more appropriate for race day conditions. It's kinda hard altering running environments and guessing about what sort of gear will be necessary, so I'm packing a few options and plan on being flexible come race day morning.
But consider that for me, 56 degrees first thing in the morning is gonna feel dang chilly. Granted, I think that's an awesome temp for running, but for standing at the start, I can guarantee I'll be chilly -- I'm used to running in temps that are pretty steady between 82-92 degrees. And as far as the high of 75? Please, our A/C in our house is set at 76 degrees. So, if I can run in conditions that will be, at the warmest, the temp of my air conditioned house, I'll be very pleased.