First of all, I can't imagine the assignor didn't have a 4th umpire available, especially since this was a tournament. There's just too much at stake in a tournament to have this kind of situation happen. I echo Peter's sentiments that maybe umpire availability was suffering, so that may have been a reason. A rush to judgement is not neccessary here.

Secondly, just because an umpire is just a couple of years older than the players doesn't disqualify him from working that game. If that were the case, then noone should be allowed to work slow-pitch softball games because the players and umpires are all the same age range. If his skills were extraordinary, and the assignor picked him for that, then that point is moot.

Third, I would discuss this with the board of your association, in the presence of the assignor. This gives the board an opportunity to hear your concerns, at the same time allow the assignor to give rebuttal if neccessary. Don't go filing a complaint or asking for sanctions right away. If the board feels there's enough for sanctions, leave it to them. Just present your concerns and the facts of the situation at the most.