Places to camp in/near oklahoma!

We were avid overlanders of colorado, arkansas, and newmexico. We even had a few epic trips to arizona and the black hills. But, life got rough, and now I get to split custody of my kids. Now with a limited budget and less gear, i really need to plan for some awesome trips when this hot weather subsides some.

What are the coolest places within 3-4 hours of northeast Oklahoma? It can be remote 4x4 required, state parks, or whatever! help a dad of 2 boys out!