Were you raised by your Grandparents while your parent(s) were still around?

We currently have guardianship of our two-year-old grandkid who I'll anonymize as "Critter". Mom & Dad are still around in the city and see the kid weekly or so. Mom is more involved than Dad who's a slacker for whom a child is too much work. Both have drug, alcohol, & financial problems (the first two cause the third) which is why we have legal guardianship.

We are seeing this as a long-term situation. We're not anticipating that either parent is going to ever be sober or financially secure enough to regain custody. (...and given the shit-show that has been the majority of the past decade, they've got a lot of proof to gather before we ever trust them again. We've reached the guilty-until-proven-innocent portion of the relationship).

Mom & Dad get to play "Disney Parents" where they show up weekly, take the kid for play time at a park & ice cream and then toss the responsibility for raising Critter back on to my wife & I. I'm not griping. It's work raising a toddler but I love Critter and I'm not upset at the thought this responsibility other than my worry that, at 60 years old, my shelf-life isn't what it used to be.

I am worried about navigating the "this is my mom but my functional parents are my grandparents" issue, though, especially as Critter is getting older and realizes that we're in a "non-traditional family structure".

It was a discussion about "We're a family" this morning with Critter that started this train of thought. "You, me, Nana, & the kitties and doggies are a family... pause... and (Great) Grandma and (Great) Granny, and Mama, & Daddy are family." (and then I choked a bit internally because I can't really endorse Mama & Daddy. Their disfunction is why we're "non-traditional".)

For those that were raised by grandparents, or those in the same situation as us, how are you navigating having the parents around while you are really the one doing the parenting? Any thoughts, tips or tricks?