I am sorry for your loss and it is tough rearing young children alone.
Financially you say you are secure which is a great relief. As the other posters have said there is no entitlement. That is not to say that you or the children wont benefit either by a will or in the absence of same.
Your husband was probably not aware of the full legal position.
I think you should just get on with your life and see what the future brings. There does not appear to be any signs of animosity in the family so hopefully as they say "whats due to you will come to you"