Lookout Mountain KOA, never been there. I don't know anything about it but seems like it's a good distance from Rock City and Chattanooga.
Raccoon Mountain CG, the best I can say is it's ok. Not over priced. Not much shade.
Chester Frost is a county park here. The good is it's on the lake, cheep, three dump stations, very nice and good space between sights. The bad is no sewer and no reservations. But if you get there on Sunday through Wednesday there should be no problem getting a sight. Not real close to Rock City, but not too bad.
Holiday Trav-L-Park has a lot of good reviews on the net. I have never stayed there.
Plan on going to the Tennessee Aquarium. Cool place.
Best fried chicken is Champy's on MLK. Home - Champy's Chicken
Chattanooga has changed allot in 20 years. Places you wouldn't go to back then, are the in places now.
Let me know where your thinking about staying and I can check it out for ya'll...