#MSWL (children's ch books ages 7-9 cont...) Maybe the boy doesn't shrink, the bugs get bigger? Also, MYTHICAL MONSTER series: boys adventuring w/creatures like big foot, Lochness, Yeti, Whatever the angle, commercial concept: stories w/animals, underwater adv, princesses, etc.
#MSWL children's chapter books ages 7-9 (with a series in mind), very boy- or girl-centric. For Boys: Maybe something about a boy who considers himself a "Bugologist" & shrinks down to bug size to go on adventures. For girls: A story about a magical doll house that comes to life?