You don't have to have a model release for that. You own the copyrights, you honestly don't need a model release unless they're under age 18, or you plan on selling the pictures.
There are a few other stipulations I can't remember them all but seriously..
Whatever course you decide upon, there is always someone to tell you that you are wrong. There are always difficulties arising which tempt you to believe that your critics are right. To map out a course of action and follow it to an end requires courage.