Greetings:

I would get something in writing from the composers, even if it's just an e-mail sent from one of their accounts. And please give them credit as the authors and copyright holders. In most programs the alt-g combination will yield the © symbol.

In the USA at least, a mechanical license is a very simple document. I've purchased quite a few from publishers or through the Harry Fox Agency, and I've also issued several myself. I've also obtained compulsory licenses in several instances by sending the copyright holder the required notice along with a check for the statutory fee, currently 9.1 cents per CD for songs up to 5 minutes running time.

At 9.1 cents, the 300 CDs would cost you only $27.30 in licensing fees for use of that song if the composers didn't waive it. I'm sure that they, their representatives, or their successors would never bother you over that piddling amount, but it's still worth having something in writing. Oral contracts may be valid contracts, but they are hard to substantiate.

--- Steve