Sandusky OH -- 55 miles from Cleveland -- may not be as famous a town for family getaways as, say, Orlando, but with some 9M visitors a year, it ranks as a player, thanks mainly to Cedar Point Amusement Park. Lately a cluster of resorts with indoor water parks has been extending the fun times through the non-summer months.
If you've ever wondered, "Where's the roller coaster capital of the world?" now you know: Cedar Point, in Sandusky Ohio, makes the claim, and has often been voted the "Best Amusement Park in the World". Cedar Point has a lakeside location on the shore of Lake Erie, about an hour and half from Cleveland. The park has a huge collection of non-thrill rides too, tamer roller coasters, carousels and kiddie rides, and live shows. Soak City water park is included in Cedar Point park too, and adjacent Challenge Park has go-karts, miniature golf, lots more.
Billing itself as an "upscale dude ranch", this B&B specializes in horse-riding; kids can also help feed and groom farm animals. Area attractions include Amish country, Mohican State Park, and several ski resorts. About an hour NE of Columbus Ohio.
Ohio has some very cool state parks with lodges, easily driveable from southern MI and western PA as well as from Ohio towns. These unique family-oriented lodges are open year-round; all feature Great Outdoors recreation, and some are on lakes; a couple have golf courses. Guests might stay in a lodge with indoor pool, or cottages in rolling hills.
Holiday World is a well-liked 100-acre theme park plus water park, open early May to early October, and located in the town of Santa Claus, Indiana. Location is 3 hours from Cincinnati, 1 hour from Louisville Kentucky. Admission includes both Holiday World and the Splashin' Safari water park; in both, sodas, lemonade, iced tea and ice water are free.
Wisconsin Dells-- with a population of just 4000-- is the indoor water park capital of the world. Over twenty resorts offer an indoor water park to their guests; some sell passes to outsiders too. A number have outdoor facilities in summer also. Wisconsin Dells has lots of outdoor recreation in summer, as well, and cross-country skiing in winter-time.
Boyne Mountain is a four-seasons recreation area in northern Michigan, with skiing in winter, and summer-time boating and fishing on lakes and Lake Michigan, plus hiking, biking, etc. Add to this mix the Avalanche Bay Indoor Waterpark billed as Michigan's largest.
Wisconsin's neighbor state, Minnesota, is likewise getting into the act with indoor water park resorts. Makes sense in a northern climate!