My DC are 14 and 16 and close to both sets of GP still. I think it helps that the GP are all under 70 (just) and relatively fit and active, they also have much younger cousins on both sides. My parents still help me out with child care, when I am working and can't manage all the school runs and extra curricular activities. Sometimes they will just pop in for a chat when they are passing to see the DC. DC can't get to there house independently as they are not on a bus route.
Next week they are taking all the GC on the annual family holiday and only my eldest DC is not going as she doesn't like beach holidays and needs to be home for her GCSE results. This year I will go along as I am not working, this is much to DC disgust as she much prefers being on holiday with the GP without me.
Also have good relationship with PIL who are particularly good at days out and theatre trips.
I would have said that both my children have quite a good relationship with my mum (my dad died earlier this year) but this sumer ds went to stay with her for 1o days and it wasn't the best experience for either of them (ds had a bit of culture shock and was then a bit upset that my mother had zero time for his current slightly obsessive interest). My mother then came and stayed with us and got a bit peevy with dd for 'trying too hard'.
Some of this is my poor mother adjusting to life without my father and some of it is the stubborn way she thinks that everyone should be interested in whatever interests her (god, gardening, opera, outdoor pursuits, socialist type politics). She has very little interest in anything vaguely popular and isn't afraid to say so!
ds is a typical lazy teen and has to be regularly booted off the computer/other electronic devices, which my mother thinks are very bad to start off with. So perhaps it was a recipe for disaster! Previously he has been much more willing to please and she has been more forgiving. I hope that they will get on better in the future, but I remember how difficult I found her when I was a teenager, s maybe not!