How about this?
I am planning to go talk to the Head Lifeguard anyway. I took a couple portraits of him while he was on-station. These pictures I do not plan to sell or distribute outside of my Flickr page. Just out of friendship, I am going to take him a postcard sized print, anyway.
What do you say I take him his picture and bring along copies of the two pics I am planing on selling?
I show him the pics. Ask him what he thinks. If the guards in the pictures want copies, they can have them.
In the mean time, I keep a clipboard and a few blank model release forms in my car.
If I need them, I've got them close at hand.