If your base coaches are only watching the ball and the defense, I would suggest getting better base coaches.
It's not that difficult for a base coach to glance at the PU in this situation and see that he/she is making the Infield Fly call. Not really different than glancing at the umpire when he/she judges fair/foul down the line. A good base coach keeps his/her head on a swivel to capture all elements of the game, not just one or two of them.
and they should be making certain right girls is at plate, and on deck, and that someone in warming up new pitcher coming in next inning, and figuring out where next game is, monitoring parents in stands,
I guess I just feel that it is really not that big a deal for an umpire to be clear in making a call, why are umpires so against this? maybe the coach is concentrating on telling his player to get back when they ran when they shouldn't have, etc.
Umpires CALL (this includes verbally) the game, coaches COACH their players (calling out IFR, batter is out is not coaching).