Making the assumption that the boys are more likely to kick the cushions around than the girls is gender stereotyping and no different to saying that the redheads, or DCs with older siblings, are more likely to.
I thought like you, once.
Then, to my chargrin, I realized that boys and men stubbornly refused to live up to my expectations. They stubbornly insisted on remaining a bunch of bullies and rowdies, respectively on committing 90% of crime, despite all the feminist efforts to change their socialisation.
There are exceptions, but on the whole, boys and men are just too lazy to aspire to escaping gender stereotypes.
I don't see why we shouldn't treat them accordingly to the stereotypes if there is NO sign at all that those stereotypes don't apply.
Yes, stereotyping is lazy. Know what? I'm lazy. And in the face of the danger of having a dozen or so children run around my house and destroying my furniture, I'd become even more lazy. Sorry.
That said, I'd draw the line at a "Make-up and make-over party" for nine year olds. Not because the poor boys can't come, but because no one should tell nine year old girls that they're not beautiful enough as they are.