It's a minefield. As has already been said, if you leave your share to your DH and die first, you won't actually have anything to leave - it will become his and then, if he leaves all of his money to his three children equally, what he already suggested will happen. If he doesn't, how will he determine how much should have been yours, especially if it's property and not liquid assets? Similarly, if he dies first, he could technically have nothing to leave to his kids, so you could leave it all to your one child.
I see the principle in saying that his children will also inherit from their mum, but again, circumstances can vary. I'm absolutely not saying that this is your own family's situation, but in general terms, consider this scenario:
A man has 4 children with a woman he isn't married to and then walks out and leaves her for another woman, whom he marries. He pays the bare minimum in maintenance, maybe arranging his SE income to avoid even that. As a single mum of 4, she is unable to date, build a career, get properly financially stable and is only ever able to rent from the council for the rest of her life.
Meanwhile, the man and his much younger wife do very nicely for themselves. They build very successful careers, get a huge, very expensive house and sizeable assets behind them and, some years later, have a child.
The man thus has 5 children in total, but the new wife only has one. He dies and, although his wife could have left the whole lot, now all technically hers, to her own child, she decides to be 'fair' and makes her own will so that her half goes to her child and what would have been his half is split between his five children.
She makes this decision on the basis that they also have a mother to inherit from, even though she will die penniless - largely as a result of having been left alone as a single parent of 4 children, by their father who has paid nothing for them throughout their lives. Fair?