I was on holiday in Playa den bossa a few years back when my children who are now teenagers were young. I thought at the time it would be ideal for teenagers there is loads to keep them busy, fun bars, bungee and an excellent waterpark.
A boat trip to Ibiza town in the evening is a must! The small boutiques are good for browsing if you have girls there is also a street market.
Be careful not to be ripped off in the bars though, we were charged approx £20 for a pint of lager, a cola, an alcoholic cocktail and a non alcoholic cocktail. There is often no price lists displayed.
I am sure you will all have a great time, I was thinking of going there again this year, my kids are now 17&16