Even though the purchase money was paid by your father, your mother would still be considered as the owner
Your father never disputed the ownership of your mother
So after your mother's demise, the property will go to her legal heirs as per s. 15 of Hindu Succession Act
The husband and children are the legal heirs of a female Hindu
So your father has an undivided share in the properties
If he has to make a Will then he can make a Will only for his undivided share which he inherited from his late wife