Christie Brinkley knows how to show up and show out, and yes, we’re referring to the gorgeous coastal-chic outfit she flaunted for a ‘fit check.’ Her look gives instant Hamptons rich mom style, thanks to a few staple pieces that are flowy, comfortable and downright flattering. We’re obsessing over the entire ensemble, but her striped top really seals the nautical deal. The supermodel was on her way to a Solving Kids Cancer benefit when she stopp…