Fly religiously on DL, but usually alone.

In two weeks, will be flying with my parents. It is a rare route (LGA-SRQ) so I imagine that as Gold, I will be upgraded. What is the likelihood of mom and dad being upgraded as well?

Do I need to ticket all three reservations together, or just tell DL they are traveling with me, etc? Also note, neither of them has status with DL.