Who do you talk to if you want to plan a small wedding ceremony at The Falls? And what are the prices?

I would start with the city of Joplin

Maybe the Park Rangers

I'd contact a local wedding planning business about that question. Since this is a state-protected, public access park, I'd think there would be a FEE to BE on the land. (Unless you're fishing.)

Yes the Chamber of Commerce or Visitors Center might have information. I couldn't find anything doing a Google Search.

We got married here 4 years ago and it was awesome,a biker style wedding my buddy road my wife on the back of his Harley Davidson down the path to me and the preacher anyway we didn't have to pay or set an appointment or anything