You keep doing that to older DnD players too, except you drop hints that the enemies are in a cult that has been giving them power and when the wizard does fireball them, the wizard gets hit by a dozen hellish rebukes from all the young warlocks they just hit.
But then you also give them terrain that would allow a clever wizard to position themself such that they can see the epicenter of the fireball without having line of sight to the targets themselves
You keep doing that to older DnD players too, except you drop hints that the enemies are in a cult that has been giving them power and when the wizard does fireball them, the wizard gets hit by a dozen hellish rebukes from all the young warlocks they just hit.
But then you also give them terrain that would allow a clever wizard to position themself such that they can see the epicenter of the fireball without having line of sight to the targets themselves
Honestly, if they caught the hint, understood what it meant, and took action, that would be a miracle and would totally be worth some cheese.