Except that something like 'the Joneses' golf clubs is a bit suspect, because there are those (including me) who say it should be 'the Jones' golf clubs'. But it's a matter of preference and convention, I think, and as long as you're consistent then either is acceptable.
So what you should be doing, Clanky, is writing about a group of adjutants-general and a children's day (because 'children' is a collective noun, i.e. there is just one group referred to, and therefore, for the purposes of this context, is singular).