I tested the full length version, made here in an ultrasoft sweater jersey with a ribbed knit waistband and cuffs. I think my choice of working with sweater jersey turned out quite nice. You can use thinner fabrics of course, but I was sure they wouldn't last one day on my boy. With this fabric the pants survived quite some tree climbing already. That's a success in my book!
The pattern includes big pockets and a faux fly with snaps (or buttons, whatever you prefer). Together with the drawstring these provide a great opportunity to add some pop of colour.