Cover yourself and get a release. Its so much easier now, at the shoot, that it will be later trying to track them down and get one. The use may be for editorial use today, but I'm sure there will be uses in the future that will be commercial in nature. Then you will be tracking down the talent to get a release, or worse, the client uses it without a release, the talent finds out, and you're both trying to reverse the mess at your expense.
In my contracts, I have a clause that states no model release exists for any talent, property, trademarks, etc., and its the clients responsibility to obtain one unless otherwise stated on the face of the contract. This is a backup just in case they say they don't need a release, than later use it a usage that requires a release. But I try to get a release and provide it to the client anyway.