Subplots aren't that bad. They branch off, and grow alongside. Hooking them into the right times and places can be interesting, but not that bad. Until they go and complicate the plot. (Which they ought to do, if they don't chime variations on the theme, and probably ought to if they do.)
But the real danger is realizing that the X you put down is insufficient explanation. If the village finally revolves against a boy who gets up to mischief one time too many, it rather matters what he actually did. And probably whatever he did has to have some bearing for good or for ill on things to come.
Of course, if you put down every detail, you aren't outlining. Outlines are really rough first drafts.