He's had his turn to frolic? He was working wasn't he, you know earning a living?
OP Devon really isn't the end of the world, I don't suppose Dorset is either. We moved her when our youngest two were 6 and 8. It is a lovely life, their school overlooks a local beauty spot on one side and a beach on the other. At CCF they sailed, as teenagers they partied on "their" beach. Someone said something about summers being good but not winters, can't remember the actual wording, actually we all prefer the winter, no traffic jams, beaches to ourselves and a mild climate so enjoyable all year round.
Lots of Europeans down here, don't know where you come from but I have made friends/had colleagues from France, Germany, Poland, Italy.
But of course London has loads to offer as well, concerts, museums, galleries. We ended up taking our kids to London to enjoy the things they couldn't do down here. Of course it depends on what everyone likes doing, if no one likes sailing, swimming, walking the moors then London would win every time.
It was only when they went off to university that my kids realised what a wonderful time they had growing up down here.
Don't feel one of you has to be right and one wrong, you both have dreams. You all know what London is like so maybe spend a bit of time in Dorset/Devon and see what you think. Dorset is obviously going to be loads better for getting back to London to see friends.
By the way Devon and Dorset aren't all rural, we have cities, maybe not as much on offer as London but you don't have to move to a tiny village. We did consider that but moved to an area with easy access to beaches/moors but close to a city in a large town, best of both worlds we felt. My children went to a good grammar school and did very well academically.