You cannot drive to the MK from Citricos which is at the Grand Floridian.
If you drive to Citricos you can valet park ($20 + tip), eat and after you are done take the monorail or boat to the MK. If you valet your car you can leave it at the GF while you enjoy the rest of your day at the MK. For either the monorail or boat I would allow about 30 minutes.
If you self park at the Grand Floridian, you are allowed 3 hours for dining and enjoying the resort. Since it is not meant for parking while going to the MK after you are finished dining you will need to drive to the TTC which is the parking lot for the MK. From there you can take the ferry or monorail to the MK. I would allow an hour to drive to the TTC-->park-->travel to the MK.
Or prior to your dining reservation you can park at the TTC and take the resort monorail and get off at the second stop which is the Grand Floridian. After breakfast take the monorail or boat to the MK.