I can definitely understand how upset you are. When someone is YOUR child or someone you know personally, there is a level of emotion and feeling none of the people on here can understand (and some are obviously not empathetic).
This is not what you want to hear, but its perfectly legal for him to do this. Its really no different than someone looking at them, except he's captured it on film. And its not illegal to do that. The law basically says that if a person is going to be in a public place wearing something that covers as little as a bikini, they shouldn't be upset when someone takes a photo of them. Obviously there's more to the issue than that, but unfortunately courts don't recognize the fact there's more to it than that, you know?
This is why dads don't want their daughters wearing bikinis to the beach-- very few 16 year old girls understand how some older men look at them. If they did, they'd probably be horrified. Now 99% of photography is created with good intentions, but as is the case with many other things in life, that sour 1% makes some of us look bad. I hope you don't think all of us photographers have bad intentions like I fear this gentleman has.
I hope nothing too bad comes of this, and wish you the best of luck in whatever happens. I would be glad he put it in a private gallery, though, cause I'm pretty sure he didn't have to. Nonetheless, I feel for you.