This is a tough situation, MB... but I can't imagine he would respond to you in a positive way. Yes, it will suck for your kids to deal with a loss if it comes to that. .. helping them through tough times IS your business... but I don't think his relationship with his gf is.
If he gets hurt you don't have to revel in it... but I would personally stay far away from this. I think it would make you sound petty and bitter. I mean, why would your friend even tell you about this? What was her goal? Is she HIS friend? Maybe she should tell him herself? I can't really tell what her angle is.
