Mandy, I think that it's something you should consider. As long as your son is prepared to go along with it, and that your XH is fully aware of any boundaries you deem necessary, then I say go for it. Burying the hatchet will be good for you. Just so he knows that it doesn't mean he gets away with not paying what's owed you, etc. and he can't take advantage of you, AND there is no 'friendship' with the OW wife. Perhaps, this will allow contact with him, rather than with her.
But, I think you know all this already, 'eh!
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim