you could always slack of AMS itself and head to Haarlem instead! Its an awesome little town, very cute shopping streets, great cafes for food and coffee. You could hire a bike there and bike to Bloemendaal en Zee, about a 15 minute ride and be at the beach! Depending on when you go the really cool beach cafes and bars may well have been built for the season, a great way to realx for a few hours before coming home!