The latter....I think.
Panel 1: We pick up the story at the store whose ads Elly hates; as Mike and Lawrence take point, Connie tells Elly, who's pushing Lizzie in her stroller, that homemade costumes are nice but this is so much easier.
Panel 2: it's a matter of going to to the store where the kid sees what he wants, gets it and everyone goes home.
Panel 3: As she declares "No fuss, no muss, DONE!", we notice that Mike clearly wants a Space Guy costume. For now.
Panel 4: What Connie clearly didn't anticipate is how changeable Mike's mind is; that's because he says that he changed his mind just as they're about to head home. Elly's response is what to scrunch up her face into what karisu_sama calls The Underbite Of Evil.
Summary: As howtheduck said in his blog yesterday, this strip serves the purpose of telling us that Connie isn't as good a mother as Elly is because she doesn't have it as hard. If Lawrence were as difficult to raise as Mike, she'd be a better parent.