OP, you should have joined the mile high club with the daughter. (Was she hot?)
I definitely would have had the FA tell the grandmother to control the kid. I've never had a kid kick my seat, but I was once on a trans-Pacific flight with a loud kid across the aisle from me (not a baby who can't help it, a kid old enough to know better) and while everyone else was trying to sleep this kid was just playing very loudly. I first asked the kid directly, then later the father, then finally an FA to get him under control. Step 3 worked.