I haven't stayed at Twin Fountains just driven by it several times. Park looks very nice, but N.W. Expressway borders the nothern side while I-35 borders the east, so I would think there's alot of highway noise.
Approx 5 miles or so south of Twin Fountains there's a few museums, Firefighters, 45th Infantry and the Omniplex (hands on science museum - alot of fun for the entire family). Also the Softball Hall Of Fame.
Next to the Omniplex is the Oklahoma City Zoo. It's a great zoo with a brand new elephant exhibit that you gotta see.
There's also Remmington Park (horse racing) next to the Zoo and Omniplex.
Go north of Twin Fountains on I-35 about 5 miles and there's Frontier City. A pretty good amusement park.
About 10 miles east of the intersection of I-40 & I-35, located at I-40 & Choctaw road, is a very nice KOA (Oklahoma City East KOA). Just in case you want something a little quieter. A little more driving to area attractions, but it's still easy to get to everything. I have stayed here and it's a nice campground with very nice people running it.
My RV dealer (Leisure Time RV) is only a 3 or 4 miles away if you need anything along that line.
Check out reviews of both campgrounds here; RV Park Reviews :: Oklahoma