Superslide Amusement Park is an old-school seasonal family stop in Bismarck, with rides and amusements aimed more at children than thrill-seeking adults. Its location by Sertoma Park and the Dakota Zoo makes it easy to fold into a low-key family afternoon.
It is not worth a long detour on its own, but it clears the bar as a useful local attraction when travelling with kids. Check operating dates and weather before going, since the park is seasonal and largely outdoors.