Bruce,
I am also going into this area with my family week after next. I have done all of these parks before with my family. (SFSTL,PKI,SFKK and HW) The park that my wife and children enjoy the most is Holiday World. It is just off of I-64 about halfway between Louisville and St. Louis.
REASONING:
1)This park has a very laid-back, family atmosphere. Less need to rush around. It's a relaxing non-stressfull environment for non-thrill ride enthusiast.
2)It won awards as the cleanest park in the country.
3)The employees are friendly to a fault. Past Awards in this catagory also.
4)Two great CCI woodies.
5)A fantastic and safe water park.
6)Free parking.
7)Unlimited Free soft drinks.
8)Quality food at reasonable prices.
9)Attractions that non park enthusiast wives may enjoy such as wax museum, doll museum and a fantastic Christmas museum.
10)Discount for entire family with one unmarked (any) pepsi can. (They have an ever better discount for ACE members)
Make sure to check the website
www.holidayworld.com This is in no way a slam on the other parks as they are all terrific. Well, maybe not SFKK. But I sensed that, like myself, you may have some family members that want to experience other things besides amusement parks. Through my experience, Holiday World is by far and away the best choice between Cincy and StL.
By the way, St. Louis is one of the best, most inexpensive family vacation cities that we've ever been to. Don't miss,
Science Center, free
Zoo, free
Grant's Farm, free
Missouri Botanical Garden's, small admission
The Museum for Westward Expansion, free (Under the Arch)
The Magic House if you have children under 12. This attraction is about 5 or 6 dollars but most hotels have 2for1 coupons.
Try to find Ted Drewes on Chippewa Ave for the best (custard) milkshakes you've ever eaten. They are called "Concretes". This is a local favorite and the long lines move very fast.
See
www.explorestlouis.com for details on these attractions.
Like I stated before, I'm taking my family on a midwestern swing in June. We'll be traveling from our home in eastern Kentucky to St. Louis on June 2, a couple of days there then on to Wisconsin Dells, SFGam and Indiana Beach.
I hope this information is helpful. I guarantee, if you chose Holiday World, you'll be thanking me later.
Have a safe trip.
DAC