I think with this relationship set up, even with a really kind, loving, supportive dh, you need to determine that you have a way of negotiating big decisions equally as a couple.
For example, if the dh in this case is offered a new job that involves a move abroad, or they need work doing on the house, it’s inevitably the one who is the highest earner who gets the most “say” in the decision. And that leads to inequality over time.
It also means that the onus is on the sahp
part of the couple to be in charge of domestic drudge, whether they have cleaners or not, it’s their domain, and that can lead to inequality too.
Also, as she hasn’t had dc yet, I would be worried that your dd doesn’t fully realise what she is agreeing to. My dh worked abroad in the early stages of our relationship and it’s no fun being on your own for three nights straight with two vomiting dc. Similarly, it’s scary having no one there if your dc has to go to A&E etc.
Now if you have serious wealth you can afford live-in help so maybe that won’t be a problem. But if you have wealth to buy the big house, but not the people to staff it, that might not be as much fun.
But it would be good to know in advance who sets the parameters of the budget and how your dd will access it?
She is making herself vulnerable to his decision-making priorities otherwise, which may be very different to hers.
Finally, I would be interested to know who instigated the idea of living in the country. As pp has said, the countryside can have more of a community feel than living in anonymous London, so I wouldn’t necessarily be worried about isolation.
And if they want lots of dc it may make sense financially to move out. So I think the success or otherwise of this arrangement will depend to an extent if your dd is a career driven urbanite, or whether she is more of a nature-loving homebody who loves ponies, lots of space, and the WI (exaggerating and over-simplifying there obviously).
Also, despite the age gap, whether your dd can speak up for herself. Having dc changes the dynamic of any relationship so much. Does it sound like her dh is willing to embrace that change equally or will it only be your dd’s life that is dramatically different?
It’s not really your place to interfere in their decisions op, and people will have different ideas about to what extent it’s appropriate to “express your concerns”, but hopefully this thread will have given you ideas about a few topics that you can chat to her about thoughtfully, that you can broach in a supportive “I want what is best for you” way?
Similarly,