I'd thought about mentioning Crater of Diamonds, but figured it might be too far away from your target area.
One thing I must mention, though, is the weather. If you come in very early June, it will probably be in the upper 80s, humid, and many days there will be periods of clouds and perhaps 30-40% chances of scattered showers/thundershowers. From mid June through Labor Day the temps go into the 90s and sometimes low 100s with lots of sunshine. I have taken my granddaughters to Petit Jean twice, always in early June. After that I don't camp around these parts... I head north to MI or MN, or to the Rockies. So what I'm saying is, if you vacation around MO/AR in summer, have plenty of air-conditioned venues in mind (especially during the afternoon hours) or be prepared to sweat a lot.
