It will be close to 6 by the time you get to the resort, then check in. Since you didn't state whether it's AM or PM, if it's PM I'd head to DTD rather than MK. Assuming you are arriving on an EMH night at MK the plan you have would work well. You could always change to a park that has the EMH night too. I also wouldn't stress that much about buses. Unless you rent a car, you have only taxis to rely on. I'd rather put up with the lines than getting lost at WDW. It's just one less thing to stress about while there, for me anyway. Others might feel differently. But keep in mind the buses are the best way to get to MK. They park closer and you only have to board a bus. With any other form you must either take the monorail to the TTC, then get to your car or ferry to your car at the TTC.