invite wording

My fh's father has passed away, but we would like to put his moms name on the invitation...should we put

#1
son of Mrs. Moms First Name, Moms Last Name


or


#2
son of Mrs. Dads First Name, Last name

It can be a very touchy subject with some people. I am in a situation where my father, due to illness will not live to see my wedding day. My family will be making the wedding. When we order invitations, they will read as follows:

Mrs. Mom's First name, Dad's Last name
Requests the honour of your presence... etc.