Given how close Thorpe and Chessington are, I'm still surprised that Merlin haven't tried to combine them in some way.
Something like stay at one of the resort hotels and get a day at each park, with a shuttle bus between them. Or even just a normal (free) shuttle bus so the family can stay at Chessington and the thrill seekers can get to Thorpe and back without needing a car, while the parent(s) can stay with the younger ones.
Could even make them electric buses charged from solar panels covering the car parks, really bump their green marketing (and I'm sure there's government incentive they can bag on the way).
Maybe even a park hopper pass like Disney, spend the morning at Chessington and the afternoon at Thorpe. Or pop in to check on the thrill seekers before nipping back to Chessie on the next hourly shuttle.
They could offer the online advance discount ticket price on the day if you're staying at either resort and decide you want to give the other one a go after breakfast.
Or even just advertise the fact there's another Merlin park less than 20 miles away! I don't remember seeing any specific marketing for Chessington last time I was at Thorpe. I get they serve different markets, but I can almost guarantee there will be some parents taking their older kids there that don't know there's also a park for their younger ones close by.
Realistically, despite being geographically close, depending on the time of day and route, that journey is anywhere from 30 to 60 minutes. It would be almost impossible to run it to a timetable and regularly without a fleet of buses which would be a significant expense. Merlin won't even operate a bus to Alton Towers so the notion of them running a two way hourly service like this is unfortunately pure fantasy.
I think that journey time and distance is beyond what families would be comfortable separating for too.





