I've lived in Oklahoma all my life, 60 years. I've seen....maybe....a half dozen tornados, none as big or devastating like you see on the news. Most tornados are much smaller and many occur in open country where damage and injuries are very limited, if any at all. If a tornado forms while you are visiting here, more than likely it will be several miles away headed in a different direction.
April is just the start of storm season here in Oklahoma. We usually experience rain showers with occasional thunderstorms. While tornados can occur at anytime, May and June are the height of tornado season in Oklahoma.
If you tune in to the local weather stations while visiting here, they do a fantastic job of keeping people updated on the current weather. That and a little common sense will help keep you and your family safe.
Most campgrounds will have some type of plan in the event of bad weather. You just need to ask what that plan is when you check in.
Think of it this way. Many people live here and camp here. While experiencing a tornado first hand can be devastating.....if tornados were that big of a problem I don't think they would.
If you make it to eastern Oklahoma.....around Lake Eufaula.....give me a holler!