If the MK will be open, then yes... that would be a good idea. The wait for the bus shouldn't be more than 10 mins... and the bus ride itself shouldn't be more than 15 mins.
Once you're at the the MK... you have two choices. First, take the Resort Monorail. Second option is the lil boat. Both options could potentially take as much as 25 mins to get from the MK to the GF.
All in all... I'd allow at least an hour for travel time. This will allow for wait time, travel time, and walk time.