The MK buses don't drop you right at the main gate. It's a good two blocks away (in city-speak). At one point you actually walk underneath the monorail tracks.
Like the previous poster said, nothing's stopping you from riding the monorail or ferry "just because." I did that with my 5-year-old son once. We had no reason to ride the monorail all week, but I knew it was something he wanted to do. My wife took our 2-year-old back to CBR on the bus, and my son and I rode a round-trip on the monorail, getting on and off at the MK station. The loop goes MK-Contemporary-TTC-Polynesian-Grand Floridian-MK.