I would make changes to Kings Island.
My first order of business would be a five year expansion that would rival no other.
Year 1: Three Coasters. Coaster #1: A intamin coaster reaching 350 feet, speeds of close to 100 mph., and having a track lenghth of over 10,000 feet. This coaster would break many world records and I would name it The Iron Beast (I liked that name, Coaster Bob). This new coaster would be located near the Beast and have intertwining tracks. Coaster #2: Continuing the family tradition Nickelodeon will get a new ride. A version of the Flying Super Saturator (not a clone). Coaster #3: A new coaster for action zone. This will be an enclosed wild mouse roller coaster themed to Tomb Raider.
Year #2: After such a large expansion the second year will be a little slower. Vortex will be painted and will get new restraints. The new restraints will be OTSR with padding. The Racer will also get a new paint job. SOB will finally have the third train running. King Cobra will also get new restraints, similar to those found on B & M standup's this will decrease loading time.
Year #3: A new coaster will be added this year. It will be a B & M Inverted Coaster. This coaster will be much like Batman: TR, very compact and intense. This will also be added to Action Zone.
Year #4: I would then look into recreating River town. First I will add a Water Coaster. This will be very similar to Buzzsaw Falls. I would also make some minor changes to White Water Canyon. The water would be cleaned, whether that means taking all the nasty water out or something else, it would be done. Then I would add a waterfall over the end of the first tunnel. I would also try and add some more boats to keep wait times down.
Year #5: The expansion will conclude with an Arrow 4-D. By this time the design will be more developed and allow for a longer better ride than it did in the first year. This will be placed in Action Zone.
With the 5 year expansion concluded I would look to hold many world records including most coasters in one park, fastest roller coaster (unless there is a 120mph+ Air Thrust), tallest roller coaster, longest steel and wooden roller coaster, etc.