"I scream! You scream! We all scream for broccoli" Hhhmmm just doesn't seem to flow.....
How about "I cuss! You cuss! We all cuss for asparagus!"?
But seriously, if this a problem with children eating poorly, their parents need to deal with it. For children who otherwise eat a reasonably balanced diet, occasional treats like those from the ice cream truck (or pedal-wagon) won't do them any harm, and can be so enjoyable on a hot day when playing outside.