I just noticed my spelling error, I meant quick (I changed it). If you have younger children...and they generally walk slower than adults, it may take you more than 5 minutes from the MK to the entrance to the CR.
What I was trying to say was just give yourself plenty of travel time, even though it is a quick walk, it still adds more time than if the bus driver will drop you right off at the CR. Also the buses do not come as often as they do when the parks are open so keep that in mind.
I try to be at the bus stop 45 minutes before my reservation time for a character breakfast or early morning tour.