A quick but probably undesirable answer is that you can add alcohol to ice cream in order to not allow it to freeze as hard. I'm guessing however that you are not looking to get your patrons drunk and to be fair I can't imagine an alcohol that would go well with peanut butter, so we won't go with that.
That being said ice cream freezes very hard when there ...
Heat the scoop?
If you are serving lots of ice cream maybe you already have one of these. If not it might come in handy. The flowing water warms up the scoop which then more easily cuts its way thru the hard ice cream.
Let it sit and partially melt, until it is soft enough. That should solve your problem! As pointed out in comments, storing it at a slightly higher temperature should prevent the problem from happening in the future.
I just made cantaloupe gelato base for the first time and had this problem too. I added a bit more sugar and some lime juice and so far it's much more edible, lol. Bitter flavors are usually basic, so maybe the acid is helping neutralize it?