Congratulations on the upcoming nuptials!

For the airline stuff you need to call group/meeting sales from your preferred carrier. CO will probably give you a 2-3% discount on the fare if you've got enough people (20 minimum) from two or more cities. http://www.continental.com/web/en-US...s/default.aspx

As for hotels I've never had to put up cash in advance for group bookings but it will depend on the property. Generally you get a block of NN rooms and have to confirm a couple weeks out. If they aren't taken then you lose the rooms and they go back into the regular sales channels.

I have no idea about cars.