I do not agree with the idea that children have an automatic right to an equal share of whatever is left by their parents'. My Mother, unfortunately, does.
My estranged sister, who was dreadful towards her for many years before going NC, will benefit from the death of someone she has deliberately spent years hurting. Mum did eventually stop sending cheques etc after years of no acknowledgements, but even though she did at one point say that she was going to amend her Will so that the sister's share went to her son, who has also lost out in many respects because of his mother, she decided against it saying that it would cause too much grief.
My nephew brought a great deal of joy to her life, and my sister used that as a weapon for a long time, and then took him away from the family and did her very best to drive a wedge between us.
I realise that this is more extreme than the situation your husband is in, but to me anything that I have to leave this World and/or those in it, will go to those that have brought me joy and made my time on this planet, that bit nicer. Easy for me to say when I have no children of my own, and my other sets of nephews and nieces will be well provided for, I know. However, I do resent the fact that my Mum worries about money/heating etc, (even though there's no need) whilst at the same time feeling that she needs to leave her investments etc. intact as a large part of 'our' inheritance. I'm no better off than my sister, though my brothers both are, but I'd rather she used the money to enjoy her time here, rather than leave it to us. She worked hard and lived through a lot to keep us fed and clothed as kids, why should she deny herself now?
I love that people believe their children owe them nothing, and of course it's true, but likewise, does a parent owe the children an inheritance?
The lack of acknowledgement/appreciation would really gall me, and I know that whatever my sister gets she'll believe it should be more. But that's my sister.
I hope that your DH holds onto it for her or her offspring at a later stage. Her response to finding out that her siblings have received a gift could also be quite telling I'm sure.