If they stay animate, you've done it improperly - that was mean, I'm sorry There could be a case made for telling Muggleborn children they are magical sooner. It might help them with Wizarding culture and acclimation. 11 is far too old for proper acclimation. They spend their whole lives at a detriment.
I think I'll pass. I'd be far too tempted to have soup and a shawl, for autumn and winter. I have a feeling that's not your intent.