Idlewild is much closer than Knoebel's, I believe about a 45 minute drive. Knoebel's is at least 4 hours or so from Kennywood, possibly even further. While I have not been to Knoebel's yet, I have visited Idlewild and find it to be an exceptional park. The landscaping is gorgeous and the park's location is definitely "away from it all". Idlewild is home to 2 coasters- a steel wild mouse from Vekoma and the junior classic woodie Rollo Coaster. There are some decent flat rides including a Whip, Paratrooper, a rare Traver Caterpillar, and my personal favorite, the TriStar. This Huss ride is like a cross between the Troika and an Enterprise. A rare find that's a lot of fun. The kids will love the children's rides, the Jumpin' Jungle play area, Storybook Forest outdoor walk-thru, and Mister Rogers Neighborhood, a real trolley ride past the characters from the PBS TV show. And, you can have Potato Patch fries here too! Idlewild comes highly recommended and won't cost you an arm and a leg.
Sincerely, Jackie Gaughan