I agree with what's been said, Dej. Too bad if the ex and his wife don't like it. FIL is your friend....and the last time I checked you're allowed to be friends with whomever you wish....whether the ex likes it or not.

I understand your desire to keep the drama to a minimum. I'd just do whatever I could to avoid the two people likely to cause the most trouble and let FIL know you're there for him. I'm so sorry he's suffering and I hope your kindness gives him some peace during this time.