I received a few hand-me-down jeans for the 5 yo which were perfectly fine in all respects, except for - you guessed it - the knees!
So, I've been patching up the knees in the traditional way - hand-sew some extra-thick corduroy patch or one of my favorite batik scraps doubled with felt padding, the usual.
And then, I came across Monster Knee Patches at Pinterest and had to make one. Luckily one of the jeans' knees was still waiting to be patched.
Seeing how much fun this is, the 8 yo, whose jeans knees never have ever ripped in regular use, wants to deliberately cut them so she can try this.
As long a she can patch it on her own, I've given her my approval.