Same as silverlining - did it once (when dgs1 was very young) but didn't repeat it. They had visitors there for the day, but were too polite to turn us away, but lesson learned anyway.
With family 1, even if I am right outside their house, which happens fairly regularly during term time, I always text first (or phone if I need an immediate answer) to see if its a convenient moment to pop in. They are very busy, both work-wise and socially, so it seems by far the best think to do. Likewise, they never pop in on us unannounced as a family, though our son sometimes does on his own if he is passing.
Much the same with family two.
We are told we can pop in any time, but in reality I know it wouldn't always be convenient for them, so I always call or text first. We see much more of them than family 1, even though both live only a ten minute drive away, but that's down to differences in their work and social commitments.
It works well for all of us.
Things were different when I was growing up, but most of us didn't have phones then, did we, so it was much more normal to 'pop by' unannounced.