Planning a family vacation is no easy feat. There are so many things to consider: adjoining rooms, price, kid-friendly dining, and perhaps most importantly, entertainment. Fortunately, a handful of family-focused resorts across the U.S. aim to at least make sure the latter is taken care of with on-site, indoor water parks; at these facilities, your tots will have plenty to keep them happy -- no matter the weather. Here are our 10 favorite hotels with indoor water parks in the United States.