I blame Mary Poppins. I've always suspected that she was the kind of demented, control-freak nanny who specialises in making parents feel bad about themselves. There's that business of putting spoonfuls of unrefined white sugar in the infant paracetamol, to say nothing of harnessing supernatural powers to tidy up the bedroom for children who are perfectly old enough and capable enough to do it themselves.
But it's the smirk on the nanny's face, right at the end of the movie, when she's packing her carpetbag for a moonlight flit and the kids are off flying a kite with their parents, that tells you everything you need to know about La Poppins's essential sadism.
Still, it's Saturday afternoon, the sun is doing its end-of-season best, the wind is up, and before I can stop myself, the phrase "Let's go fly a kite" tumbles from my lips.
"It's very windy," says Clara, with a delicious shiver. "What if we get carried off right up into the sky?"
"Don't worry," I tell her. "If I see you heading up through the atmosphere, I promise I'll grab the string."
"But what," persists Clara, "if you get carried off?"
"Oh, come on," scoffs Con, not meaning to be unkind. "It'd take a hurricane to lift Mum."
Up on Parliament Hill, the sky is gaudy with neoprene and you can hardly hear yourself speak for the razor-whizz of stunt kites doing their stunty things, while small children beg their parents for a go at holding the control reels. It soon transpires, however, that we have got the Wrong Sort of Kite.
Out of its carrying case, it turns out to be a pointlessly complicated construction with wing struts and propellers and God knows what.
The "Let's go fly a kite" tune is running in my head (with the obvious rhyme kite/shite appearing more than is necessary in my re-worked lyrics) and I am a string's breadth away from losing the will to live, what with running down the hill a hundred times in kitten heels trying to get the damned thing airborne, when a super-smug dad in special kiting gloves - what is it with men and kit? - suggests that we might try running into the wind instead of away from it.
It's irritating advice, but it works. Clara and Conor yelp joyously as the kite finally soars and I find myself shouting, rather louder than I mean to: "And spit-bloody-spot to you, Mary Poppins!"
Conor is delighted by the mild obscenity, but Clara is appalled. "Mummy," she says in shocked tones, "what do you mean?"
"Nothing at all, my darling," I assure her, as the kite, in response to some spiteful, nannyish instruction from the ether, decides to dive-bomb Conor, running him to ground and tripping him up in a lake of mud, which I could swear wasn't there two minutes ago. "Let's get this beauty back up, shall we?" I suggest. "Quick, before the wind changes."