I don't think that parents do neccessarily understand everything that goes on in their children's lives. Also, the way the Marlow 'rents are written makes them seem realistic from the perspective of Nicola & Lawrie - they don't understand why something like being chucked out of Guides is such a big deal.

Also, I always thought the Marlow parents weren't that old. I can t remember which book its in, but I had the impression that Mrs Marlow was only about 19 when she got married - assuming she had Giles about a year afterwards, that males her only about 40 when the books are written (and I always did wonder if maybe there was a shotgun wedding and that s why Madam Orly objected to the relationship so)