Britney Spears' Sons Sean Preston & Jayden James Seen Out on Grocery Run

"Circus" in Aisle 5! Britney Spears' boys, Sean Preston and Jayden James Federline, were snapped running errands in a rare public outing together ... and look how they've grown! Sean, 20, and Jayden, 19, were seen out in Calabasas, California,…