Jodi How is the 100K setup? Are you going to be able to meet Bruce throughout the race? I think that in the rain it will be very important for him to switch to dry socks, shoes, and potentially dry clothes every so often.
Also I ran Baltimore in the rain and found that while I was hot and sweating a lot early in the race, that once I started slowing down and doing a ran / walk near the end I got very very cold. I really wished I had someone to hand me a long sleeve shirt or a jacket.
Oh, one more thing but wet clothes chaff like crazy, especially on the man nipples.

I'm not sure if one application of body glide will last for 100K.