I'm also fairly certain that there is a bus from MK to hddr. I've never taken it, but there is one to WL, because some folks can't take the boat, so I'm pretty certain there's one for Ft. W too. It won't be quite as fun as the boat, but it may well be faster, especially since you only have to get off your bus and get on the next one - as opposed to a having to walk all the way over to the boat launch, and waiting for the bus. Always ransportation take s longer than you think - so this would certainly be somethign to consider if you are running late. Remember, the boat stops at WL before heading to Ft.Wilderness in both directions, so ti will take a while vai boat to get to FtW.
To get back, - sorry had to edit this after I reread your post - They won't let you go back to MK after it has closed, esp that late (unless it's and Extra Magic Hours night). To get back, the fastest thing would be to take a taxi. Otherwise, if MK closes at 8, Epcot almost always closes at 9, and MGM will probably be closed too. AK usually closes by 6pm, unless it's EMH, and even then it may be closed by 8pm. They will only let you board a bus to the EMH park (if it's open), or DTD. (the EMH park may well be MK that night). Whichever park they allow you to go TO, you will be able to get a bus from there back to CSR. Just ask the driver which # stop is for CSR when he drops you off. It will be very close to where he/she drops you off.
A taxi won't cost very much - about $10 plus tip, I think, unless you have a large group, and then it could be closer to $40 with tip.