Hmmm Kinglake and Marysville in the one day might be pushing it. May I suggest one or the other with Marysville probably being the better option. 2 hours up and 2 hours return in cruise mode. Don't forget you need to allow time for meeting up, lunch and the usual stuffing around in a group. Just a suggestion since it sounds like you may not have done this trip before. But I will leave it up to you. Regards