Straighten out the situation with the rights, first. Establish who owns what, so that if your buddies decide it's not right for whatever reason, you still own the right to do things with it. If it's a joint contribution (eg you did the coding, but you all3 came up with the idea and your buddies each suggested things like site names and design elements), then work something out now. Even if they are cool and 'nah, it'…
Another point of anigbrowl's I'd like to emphasize: write the first draft yourself. Discuss transfer of IP from them to you, then write the doc yourself. Two reasons: 1) they don't sound like they'll get around to writing it. 2) You can anchor the agreement however you want it, and they will have to respond to edit.
I never have understood people who ask somebody else to write up the first draft of a contract / agreement. Yes, you will negotiate on points, but if you are the original author, everything is anchored where YOU want it to be.
Anchoring is a VERY powerful psychological tool.