I guess it depends how heavy your bags are, how much you want to save money and how tired you are. You can use the subway quite easily: From Tokyo Station catch the Marunouchi line to Ginza, change to the Hibiya line and that will take you straight to Roppongi (Grand Hyatt). 4 in a cab should be fine, but might cost you a few thousand yen.

With regards to Disneyland, you can catch a train to Maihama, without the luggage this would be no problem. I would speak to the concierge for more info. Have fun.