The issue is the dependency of the children on their late mother.
If the contesting of the splitting of the assets is going to be done under Western Australian law the children are automatically entitled to a share.
The following link is from the Administration Act and determines who receives what under intestacy, which means if a person dies without a will.
It is point 2 that you need to look at.
Her husband is entitled to the 1st $50,000, Interest at the rate of 5% per annum from the date of death until he receives his entitlement, one 3rd of what's left and the balance will be divided equally between her children.
This is the said amount under the rules of intestacy.
If either party wishes to dispute the shares, they have to show that they are in greater need and then it will be up to the court to decide.
The children of the deceased are going to have to get their own solicitor in Western Australia to represent them and lodge a complaint with the current husband solicitor advising that they will be contesting any application.
Their solicitor will need to ask relevant questions about the value of the estate is and can also write to the superannuation fund notifying them that there is disputes that they do not distribute any money.
Do they have a solicitor of their own in Western Australia?