It's worth looking at Mom and Dad’s name choice from a different perspective: it might have been a joke in the moment, but it also seems like
Moby-Dick was a central part of their early relationship. It doesn’t seem, from this view, that they were trying to curse Ishmael. Ishmael’s insistence that he’d be happy and normal if he had a different name reflects his youth and immaturity—as he’ll soon discover, he’s not the only teenager who struggles with his identity.