In Michigan,
Beyond what has already been mentioned are the many fine vibrant clean family friendly very affordable Beachtowns in West Michigan on Lake Michigan with gobs of activities for all constantly. Since the thread OP lives in dry Tucson, Arizona it will be something very different and special to him/them. The Great Lakes are true inland seas but with no salt and nothing that wiil attack you or bite you and the fish are delicious. No iodine taste like in salt water fish. You can drink the pure waters just like over 50 million people do from the Great Lakes. The continous pure sand beaches along West Michigan are annually rated as in the top 5 in the USA and several major world travel publications rate them as in the top 5 in the world. There are many busy public wide beaches and lighthouses and very secluded "world of your own" public beaches. Islands to explore and huge 1000' foot ships to see and thousands upon thousands of pleasure boats and sailboats. Lake Michigan alone is 100 miles wide and 340 miles long and 923 feet deep of pure water and most of it has a pure sand bottom. The water is so clear that we can often see the bottom at 30-50 feet deep when the surface is smooth.
Being at the top of a sailboat mast in the middle of Lake Michigan and looking either east or west (the short way across the huge lake) you couldn't even see the shoreline or tall building on either side and Lake Superior is nearly twice as large. The pure sand along Lake Michigan only occurs in two places on the Planet Earth. Here and in Australia and it's long been documented in Geography Books. Full of fish like many species of salmon, lake Trout, white fish, brown trout, walleye, lake perch, and many more waiting to be caught and eaten. Charter fleets going out of nearly all the ports or rent an equipped boat and do your own thing. So much to do everyday and so little time! More than 150 lighthouses in Michigan alone and 35 of those are in West Michigan on Lake Michigan. Example link: http://www.lighthousesoflakemichigan.com/
Thousands of RV parks and campgrounds, so many huge sandunes, and so much to do without sucking your wallet dry.
Example link: http://www.visitgrandhaven.com/
Another: The large very special Meijer (pronounced, "Mar-er") Gardens and Sculpture Park in Grand Rapids (30 miles inland) is world renowned and very highly visited as it's one of a kind. So much to do and see in Grand Rapids.
Link: http://www.experiencegr.com