Other mistake: When the family is leaving and the door is shut you see the floor lock (common in older homes) on the door engage. When Brad goes back in through the window you see him run down the stairs. He gets to the door and unlocks 2 locks on the upper part of the door but not the floor lock.
Continuity mistake: After Charlie shoots April in the ass with the slingshot, she immediately turns around to see who did it. Charlie is holding it as he says "Oops" and Brad takes it from him, all the while April is turned completely towards them. Couldn't she see it was Charlie and not Brad?