It's very close to Birmingham Airport - about a 20 minute drive (certainly you can fly to Birmingham from Cork) .. East Midlands wouldn't be that much further away either, but not sure you can fly there from Cork.
Perhaps it's close enough to Birmingham Airport to just get a taxi if you wanted to avoid the hassle and expense of hiring a car with child seats etc. If there's a morning and evening flight from Cork you could likely do it in a day trip too if the only reason for the trip was to visit the theme park you'd easily have enough time for a full day there and fly back the same evening.