Sounds to me like you have a good plan! Being with a team will really help you and your family enjoy the event.
The temps in Iowa during the summer can cover a wide range, to be sure! Evening temperatures can range from the 60's to 70's, or maybe into the 80's! Usually, just a light wieght sleeping bag will be perfeclty adequate. Funny, sitting here thinking about it, I have never paid much attention to the temperatures, I always slept well at night, and if it got hot during the day, I just drank more water, spun her up and enjoyed the ride.
I don't know if you have seen my pages that I did on my adventures, but if you are bored, you can see them at
http://home.atcjet.net/~whitlow/ragbrai.html and
http://home.atcjet.net/~whitlow/ragbraixxx.htm
Seems to me that I read that everyone who has applied will be getting thier wristbands, so hopefully, you will be seeing yours soon!