KravtZIm not saying a little detuning under foot hurts but this kid hasn't even ski'd park before? How do you know he will even get to the point of being able to slide rails let alone spin, swap, land hard on them? Its a really is job to do at home no need to take it to a shop. But why would you give up your edge for all mountain when you just decide you are going to become a park skier? Unless your really hard on your skis I have found they naturally detune. Then again when I tune my own skis I never really sharpen the edges to hard underfoot for this reason. But hey..to each his own
You don't have to completely grind down the edge you realize? You just want to make it slightly more rounded underfoot instead of being very sharp which makes it less likely to catch.
Also if does ski park and realizes that he doesn't like it he can always just tune the edges again and then they'll be good for all mountain again.
You can just about always tune a detuned edge (unless it's completely ground down) but you can't always tune an edge that has been ripped out of the ski.