What is the irony in the greasy lake

Perhaps the main irony is within the characters themselves.
 They like to think of themselves as "bad characters" and go to Greasy Lake because it is a place
of darkness and danger.  The fact that they are not actually bad characters at all is proven by
such things their vehicle (parent's station wagon) and their horror after the true greasy
character they hit with the tire iron falls to the ground.  They are shocked and terrified by
their own actions. At the end of the story, the two young girls ask if they want to party with
them, but they want nothing more than to slink home as quickly as possible to lick their wounds.
This is ostensibly a kind of coming of age story, or at least is drawn along those lines.
 Ironically, however, the characters learn nothing from their experience.  Their only concern is
getting out of there as fast as they can.  No remorse is expressed, or even concern about the
dead body in the lake.