We live about 20 minutes from Idlewild and have had season passes for the last 3 years. My children have loved it. My oldest has gone since she was 2 years old. There has always been plenty for her to do and enjoy. This park is very well kept, it has a lot of shaded areas and seems very laid back and relaxed. I would not recommend travelling to this park on a Monday if you can avoid it. Monday's are the day that season pass holders can each bring in a guest for free. So .... it can crowded on those days (not Disney crowded ... but still). There are a lot of attractions geared toward the younger set. My husband and I always laugh because the arm bands you get when you pay at the entrance have written on them "Voted #2 Best Kids Park in the World."
Wonder who's #1? 
It truly is a great kids park.