Yes, it is a 3,5 hour+ bus ride one way, so you will be spending 7+ hours that day just sitting in this bus seeing the "Autoroute" pass by and that is not an enchanting sight and leaving you very limited time to explore the parks. Each to his/her own, but I don't think that is a nice way to spend a port adventure and no way to spend so much money on it. The French coast has a lot of beauty and history to offer too. If you insist on going to DLP and want to experience some rides that day this kind of VIP-arrangement will be the way to go or you will have to be in a lot of luck to hit a low-attendance day.
Disneyland Paris needs a 4-5 days visit to properly explore and enjoy, so going there and back again from Le Havre is a waste of time in my honest opinion. It's become 1,5-2 major gates. If you wish to visit the resort: do it before or after your cruise, enjoy it with all the time you wish and maybe add a visit to Paris, which is a wonderful city and only a 30min train ride from the resort to the city centre. We live a 4h car drive from DLP and we never do a one day up and down.
