TBH Peacelily if you'd posted asking what people thought about you passing your inheritance from your ex mil to your son and daughter, I'd have responded by saying that in your shoes I'd refuse.
An inheritance isn't a right, it's a gift and when a beneficiary gives theirs away, they're going against the wishes of the deceased.
I agree with thatbags and lionpops, from what you've said this all started over money and even though you've forgone your inheritance your daughter still isn't satisfied.
To wait for 20 years to tell you she's been angry with you for 20 years over the breakdown of your marriage to her father is ridiculous.
I've been told more times than I care to remember in the last 4 years that we've been estranged from our son that 'life's too short'. Well, what I've learned having tried to repair the damage done to our relationship is that yes, life is too short, too short for taking undeserved crap.