Keep in mind that in Orlando, it might be 80-something degrees or 50-something degrees nearly any winter day. So you may end up with a warm day anyhow. I have been when it is cold out. I'm very wimpy about cold, and I just stayed in the water, getting out only to run to the next body of water. The water tempatures are all controlled, so they are consistent. It's wearing the wetsuit -- aka full body air-conditioner -- that was the worst for me!
I suggest you go and enjoy it. DC is really great to experience.