These stranded mittens are sized just like my other children’s mittens.
They are 48sts. around, and can be knit with fingering- or sport-weight yarn. With the gauge listed on the pattern page, they should fit 3-5 y.o. kid. With sport weight yarn and larger needles the mittens will be fine for 7 - 8 y.o. The pattern is in pictorial form with full-color charts for hands and thumbs; there is no written instructions.
For adult-sized patterns with oaks, check these out: Oak&Acorns mittens and socks.