X3 on Alum Creek SP. We've stayed here two times. Sites are all cut back into the trees, offering a visual privacy screen from neighboring sites. Drawbacks include a somewhat limited access to shower houses, and sources to fill your FW tank. Access the campground map to select a site which you feel is conveniently located near the showers. Water stands in each CG section do not offer a threaded spigot. FW with a threaded spigot is available at an approved potable water service next to the dump station. These are located near the entrance to the park.
Cross Creek is nice, but if your planning on activities at the zoo and COSI, you might not have the time to take full advantage of the added amenities offered there. As you might expect, these amenities come at a higher cost than the SP campground.