Mine also calls my parents “X太,X生”. My parents don't mind about that or I must say they prefer that more. They would feel even worse if they must call each other 親家奶奶同親家老爺.
However, my sister's in-law request my parents to call them 親家奶奶同親家老爺.
If your parents don't feel that comfortable about that, you should ask your husband to handle it.