Just ask him directly why he is doing it? Maybe he is lacking something ...try to get it out from him and work on it...everything will be alrite..

I don’t think anything wrong in that as long as you both have time for each other...you are saying that he still love you and kids….
if he was ignoring you then its a different story..

As per the recent survey infidelity is more dangerous than physical..Anywayz..all the best for a happy life.