We have been staying at Fillenwarth Beach Resort since I was a kid and my dad's family had been going since he was a kid. It is in Arnold's Park the town which includes Arnold's Park the amusement park. There is one roller coaster here and it is not scary by any means, there is only one big drop so its great for young kids/teens who are afraid of scary roller coasters. There are many kiddie rides and games to play. Plus the food is like carnival/amusement park foods, pizza, hotdogs and popcorn etc. In the shops outside of the park there is a restaurant that sells nutty ice cream bars that you MUST try!!! The reason the 4th of July is so much fun is because there are parades, very small by kids who made Patriotic themed crafts to wear around the area, mainly in Fillenwarth. Then there are nightly concerts leading up the week before, with kid friendly bands that parents love too, a favorite is Corey and the Fireflies. The walk from the resort the to park is about 10 minutes as the most and there is the central emporium in between that has so many fun okoboji paraphernalia clothes and souvenirs. There is a great restaurant off the emporium too, it overlooks the lake. There are 'Queen II' Excursion boat tours given off the dock by arnolds park that should be taken or fillenwarth gives a tour on their boats, your choice of a family tour or a booze cruise-not kid friendly but nice for the parents. My parents let us run wild here, it was so safe but we usually buddied up with a classmate to make things safer. I plan to take my kids here when they get older and after swim lessons. Life jackets are available for free at the resort last I knew or buy them if you stay elsewhere so make sure to have to little ones put one on to be safe.
It is by no means Disney, but it is a perfect sized park for a family. You don't have to deal with overwhelming crowds or lines which is great, especially when you have younger kids. It is right near Okaboji, which is a nice tourist spot with many other activities.
Arnold's park sits near the Okoboji Lakes and is a big tourist attraction! It was built in 1889 and is one of the longest operated amusement parks! It features classic rides, shops and dining on the shore of Okoboji Lake. They even feature a wooden rollercoaster, known as the Legend.