I don't thik the OP has anything to gain by reporting him, in fact the shit hitting the fan will affect the lives of all the 3 adults involved and, more importantly the children, who have already suffered enough trauma with the illness and death of their Mother.
The OP has ended the relationship and needs a bit of calm and space to "lick her wounds", she does not need the worry of possible Inquiry's/Ethic Commitee Hearings, neither do the Psycologists children need this, please think of them!!!
We don't know the bloke do we, yes he behaved badly , yes he probably got married again too quickly after being bereaved, but we don't know if he felt obligated to carry out his late wife's wishes, and its not what he really wants.
What I'm trying to say, its not all really very black and white is it, technically he didn't "date" a patient and it was after her DD's treatment had finished so although his behaviour was morally wrong was it legally wrong?
I dont think if the OP has finished the relationship, she should "reveal all" it will do HER no good whatsoever, and possibly there could be repurcussions that could cause her more hurt.
Whats more her friend, should butt out!