[Rog]

your dedication to the youth is commendable, and understandable; but, unless you are in superb condition you don't even want to think about working the plate.
Trying to get up and down to the level of these players for as many times as it may take over 5 games = OUCH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!

At the risk of being redundant - this is way too much for one person to do in one day (or to be expected of).
Definitely see if you can reduce the time limit at the very least.
Though I would not call the zone any different than any regular game. To change the zone is not fair to those players who can hit, and have a reasonably good understanding of what to look for in a pitch.

Lastly, the shortage of sports official knows no geographical boundaries.....