Panel 1: We see Mike in the bathroom grabbing a towel.....
Panel 2: ...and tying it around his neck like a superhero's cape.
Panel 3: He then hits us with the theme from Batman. Too bad Lawrence wanted to be Batman too.
Panel 4: Mike's suggestion that Lawrence be Robin doesn't fly.
Panel 5: Elly then suggests they be different superheroes. Upon being asked which ones, she says to use their imaginations.
Panel 6: Mike's imagination leads him to create the fearsome heroic identity of Burpman. This gets Lawrence laughing.
Panel 7 They laugh even harder as Lawrence calls himself Toot-man.
Panel 8 The result: Elly lectures them about how superheroes do good stuff, not stupid stuff. Back when this was suppsedly set, Tony Stark wasn't into jailing his friends and Peter Parker hadn't sacrificed his marriage to the Company Equivalent of the Devil so I'll let her ignorance slide.
Panel 9: Mike explains that the names they chose are funny. Elly shuts him down.
Panel 10: We next see her in the washroom laughing her head off. The reason she didn't let'em be Burp-man and Toot-man is obvious; finding out that she's almost as immature as they are would wreck her credibility as a disciplinarian.
Panel 11: Good thing for her that that sails over their heads. Laurence's musing that if everyone was laughing, they could save the world misses the real point: Elly does find things funny but won't allow herself to laugh for fear of not being taken seriously.
Summary: Enjoy this brief moment of your mother laughing at life's absurdities, kid. Given her hang-ups, it'll be one of the few times you do.