There are several ways around this. Being an elite level member, I have always found airlines accomodating to blocking 1 seat next to me- whether beside, in front or behind. You may wish to request this. You can't ward off anyone around your seat, but you can request a less crowded seat in the plane to get in more work or rest.

If kids kicking the back of your seat bother you, take the last row in the plane. If you don't like the possibility of doing dental work on the guy in front of you, take the first row if possible.

Here's a real kicker (no pun intended, ha ha)
Airlines will reserve the first part of their coach section for families and others requiring special assistance. Keep this in mind when you think that just because you are the front of the plane, you are with other elites and among the first to deplane after landing.

Now here's a question I have, I use upgrades to get away from these problems of space but find kids flying in First class who are twice as rambunctious. They are chase each other in the hall and climb over the seats. And they are smart too because they will do this quickly while the FA is going back towards the galley. Any suggestions?