I'm glad to say this situation is pretty alien to me. Both sets of parents went with our respective offspring to view houses when they moved so knew what needed doing in the one they chose. We all enjoyed hearing their plans and helping them with jobs and seeing it transformed.
Youngest DD is 200 miles away so not quite the same when she and SIL moved but they knew we would be perfectly happy seeing the house in a state of disrepair, would bring our overalls and muck in, and get the fish and chips for lunch.
True, it might not be the same with second marriages cos each partner has different life experiences, skills and expectations so maybe my view is too simplistic.
People are all different. But if you want to maintain relationships you have to go with the flow, even though it might not be at your preferred pace, or you might be permanently excluded.
No, it wouldn't suit me one jot and I'd be equally hurt, but not a lot you can do about it.
However, now you've got the invite, go along, smile, express approval at anything you can and have a great day.