A simple written agreement is easy to write. Include the things that are expected to be delivered and leave space for additions. You could write a one that covers as many scenerios as you can think of and if the establihment doesn't like something in the contract, they can initial it (you too) and void parts of it.

Bring up the contract talks quickly (read casual), as a normal course of doing business. I tend to shy away from any business or person not inclined to sign something. If their word is their bond, a signature shouln't get in the way. Tell them you need it for your accountant (or just Tax purposes).

My only rule is: A contract is for me -- to remember what I said.