Durwood, please don't tell me you are coaching a rec league...
I don't believe in chasing unicorns. And the backhand in softball is the biggest, brightest unicorn around.
Simply count the number of errors by your infielders and the number of times a kid *might* have made the play had she known how to make a backhand. The ratio will be something like a 1000 to 1.
First, teaching kids how to backhand a ball when their kids can't field a normal ground ball makes no sense. Every time I go to a softball game at any level, I see at least one muffed "ordinary" ground ball. If I go to a rec game, I see a bunch.
Second, the number of balls where there is a chance to make a play using a backhand are few. With the corners playing in, the only balls that are going to be backhanded by the corners are foul balls. Middle infielders should be taught to 'circle and charge' rather than attempt a backhand.
Finally, this aint' baseball. If a player has to make a backhand, the batter will be safe anyway. The player doesn't have enough time to adjust herself and make the throw.
If I were a parent of a middle infielder, I might teach the backhand to my DD "for fun" and to impress a coach. But, as a rec league or travel coach, it is a waste of time.