My favorite credit card perk is bringing friends and family into lounges for free as guests.I love letting my kids go to town on hot chocolate and treats during long layovers and hearing their decided opinions on the lounges they've visited. (Their take: The Capital One Lounge at Dulles International Airport (IAD) near Washington, D.C., has the best food, and the Escape Lounge at Rhode Island T. F. Green International Airport (PVD) near Providen…