A pirate, a space alien, a flapper, and the Mad Hatter. These costumes are great on their own, but if you're trick-or-treating with little ones you ought to look at these amazing family costume ideas. Our Back to the Future, Grease, and A League of Their Own costume sets will satisfy your film geek within, or go with the kids' favorite—Harry Potter. You can never go wrong with classic mummy or pirate costumes sets either. Happy Halloween!