There really is an easy remedy for this on many aircraft - just look for aircraft with double row Emergency Exit rows! Select a seat in the forward row and Viola! - no kids behind you
Not only this ... but no kids next to you either
Of course on those flights where the EE row is only a single ... just select the row in front. You may still be seated next to a small one, but guaranteed (as per FAA regulations on Emergency Exit seating) you won't have one behind you.
GMF