Estate Law Questions? Ask an Estate Lawyer.
The loan is a debt of his estate. The security interest is his share of the property. If the property will be going to you, then there would be no reason why his children would be responsible for the loan. If his share is going to them, then they should contribute. The loan should be transferred into the name of the new owner(s) of the property or refinanced.
You would pay half. They would pay half. You can collect and demand payment.