Parents visa


#1

I am planning to invite my parents to US to show them around.
My mom got her visa 10 years before and its expired.
My dad’s visa got rejected twice 10 years back.
Now I have to apply for Visa for my Dad and Visa renewal for my mom.
I have questions regarding this:
1.Should I take one visa interview for both of them (or)
Should I take visa interview appointment for my dad and apply for visa renewal for my mom

2.Which one is allowed?

3.If both are allowed,which one will be better?

Thanks a lot in advance.
Please respond.