A couple of thoughts from the other side (I have young kids, and my parents are around):
I’ve really appreciated some of the well-timed advice I’ve gotten from my folks. And there’s been some advice from friend’s parents that maybe wasn’t well thought out.
I think the main differences are intent and their familiarity with our family, especially the kids. My parents have enough respect from me, and have spent enough time around my house and children, that their advice can be really insightful. There’s some things my wife and I are just too close to the situation to see, or have become accustomed to that aren’t really the best way to go about things.
Thinking it through, I think general advice about things like teaching or juggling multiple priorities are pretty safe. My dad’s advice about making sure I take time to treasure my kids when they’re small and to take pictures not only for myself, but for them later, are things I appreciate the nudge from a more knowledgeable source on. My mom’s memories about teaching my brother and I to read are gentle pointers in how we can make sure we’re taking the time.
More specific advice, especially in the moment, isn’t going to be as successful I think. Discipline is especially tough because it’s all woven together with behavior in general, consistency, and just the feeling that bad behavior witnessed brings judgement.
But watching how “grandma” interacts with the kids, or stories about how they dealt with us growing up are plenty welcome. We’re just doing the best we can, and they’ve already been through it.