That is not on and yes things could really bad if he is reported. Sexual harassment is something your DH will want to have to deal with nor will the resort want it.
No matter how good someone sounds it's not until they are employed do you reall know what they are like, unless you know them before hand

I would get your DH to give him a warning, in writing, sending a copy to the GM also and then get rid of him if he doesn't improve his behaviour.

Do you really want him as a friend if he is like this. You can still be friends with his patrner and children.