Pick off all the fruit while it's immature, well before it becomes edible. Or chop the trees out and replace them with non-fruiting type that also produce no nectar that the bats find attractive. Or erect nets clear of the tree and which go down to almost ground level; these will keep away destructive birds, too. Or fire a gun into the air near the bats to scare them every 8-10 minutes all through the night. Or sell up and let the new owner worry about the problem.
If it is only one or two trees, you could try buying a boxful of rubber snakes and threading these up among the foliage. I suggest that you move them around every few days so that cluey birds and bats don't come to realise that the snakes are immobile and dead. A dab of fluorescent paint in the eyes of the snakes might make them glow more fiercely in the moonlight.
HTH