Mary Pope Osborne celebrates July 4th, the most American of holidays, with a warm family story. Three generations enjoy parades, popcorn, "Yankee Doodle," and at the end of the day, lightning bugs and fireworks. "Then I blow out the stars, as if they were candles on a giant birthday cake" --a glorous image in Peter Catalanotto"s glowing and buoyant watercolors.