Neither OK nor OH have an inheritance tax - very few states do - so the children in thoise states do not have to pay any taxes on their inheritance. Now, both OH and OK do have ESTATE taxes, so don't be confused - the difference is that with estate taxes the executor is responsible for making sure that any estate taxes are paid out of the assets of the estate prior to distributing the remainder of the assets to the heirs, wheras inheritance taxes are the responsibility of the heir.
FYI - here is a pretty good web site that summarizes taxes by state:
Taxes by State