This. People don't talk about pension plans that often, but they should.....they really should.

And then health insurance. 6 members of a family, albeit 4 of them are still underaged, it's going to be a loooot. Did someone else mention dentists? Swiss dentists? 4 kids could mean at least 2 or 3 orthodontic treatments. I don't want to scare OP off, but she'll have to take that into consideration too.

Where I come from, some decades ago these types of treatments weren't that common, unless you had a more serious problem. OH had to do it in his late 30s here, imagine that. It's at least 15k for adults, if you don't count dentist visits. It's cheaper for children of course, depending which type of treatment you choose. But oh boy, how expensive these dental treatments are. They'll have free dentist visits for kids under 18 though. I'm not sure that fixing your problems in France is always an option, as it implies a lot of....logistic. She should be planning her expenses for CH imho, not for shopping over border (see corona time), not fixing teeth over in Fr, Ge. Budget for here.

She's used to live in a large house over there, would she be happy to downsize? I personally never lived in a huge house so for me it was simple, but have seen many folks here complaining a lot. Living in a large family house is a dream here, unless you move to a more remote place and then the schools and the kids courses etc over there can be Ok, or can Not. For your needs at least. Or you're willing to part with a large amount of money, in case you actually have that disposable income.