I don't think I can help you with transportation, but I can tell you what the parks are like and what rides are the most important to hit up. Cedar Point is my main home park and Kings Island is my secondary one, so I know these parks very well. Let me just say: Alton Towers will feel small compared to these giants. Their skylines are MASSIVE. As you probably know, this trip is a roller coaster lover's dream. Here's some info on both parks.
Cedar Point
Length of Stay - 2+ days
Top Rides - RMC Mean Streak (it will be open in 2018), Millennium Force, Maverick, Top Thrill Dragster, Raptor, Magnum XL-200, Valravn, Rougarou, GateKeeper
Park Strategy - If you can afford a stay at a Cedar Point resort, I would definitely do it since you will be able to do Early Entry, when you can enter Cedar Point one hour early to ride Valravn, Millennium Force, Maverick (not listed on CP's website but I'll find out opening weekend), and GateKeeper. These rides can change every year. This is a great time to ride rides with minimal wait. Cedar Point's lines can get VERY long. How I always do my CP tour every time I go is that I start at the front gate (get there at least half hour before park opening or Early Entry opening), hitting Valravn, Millennium Force, Maverick, Magnum XL-200, Top Thrill Dragster (if it's open; if not, do it in the afternoon), Rougarou, Raptor, GateKeeper, and Wicked Twister. Obviously I'm a Cedar Point vet and those are the only coasters I have a need to ride (also have no clue where RMC Mean Streak will fit into that in 2018). You should get all the coaster credits since you're a first time visitor. I suggest 2+ days to be there. I would also recommend trying out their flat rides like Skyhawk, MaXair, WindSeeker, and Power Tower. Personally, my top five at Cedar Point are Maverick, Raptor, Top Thrill Dragster, Millennium Force, and Rougarou. Everyone's opinion is different.
Kings Island
Length of Stay - 1-2 days
Top Rides - Banshee, Diamondback, The Beast, Mystic Timbers, Firehawk, Vortex, The Racer
Park Strategy - Now Kings Island's park tour is a little more laid back, especially since the longest line I've had at Kings Island was probably a 30 minute wait for Diamondback on a Saturday. Kings Island also has Early Entry, but it only takes passholders and only lasts 30 minutes. I would suggest either going to Banshee or Firehawk first. Firehawk has bad dispatch times, so hit it before the lines get long. I was the first train of the day last time I went. You can hit all the rides as you please without any certain order. My top rides at this park are Banshee, Diamondback, Firehawk, The Beast, and Vortex.
If you can do Fast Lane for any of these parks, I would suggest Cedar Point. Both parks are amazing and will blow your socks off. Happy travels!