OK, there is a place called Sportsman Lake Recreation Area just outside of Seminole. This would be about an hour and a half from OKC and 2 hours from Tulsa.  
Check out the website, and let me know what you think.  They have a pavilion with water and electric, and plenty of fishing spots around the lake.  I thought of this place because I've been to a retreat nearby at St. Crispins, which was beautiful, but I have never been to the lake.
http://sportsmanlake.com/index.html