If you're driving, doesn't make any difference which park you're at, just drive to the Grand Floridian Hotel (which is where 1900 Park Fare is...the hotel is on Bay Lake, but it is not IN the Magic Kingdom.
If you're using Disney transport, and have flexibility on parks, it's probably easiest to be at MK. But if you want to avoid MK due to crowd size that day, your 2nd easiest would be Epcot.
If you're in Epcot for that morning/afternoon, you could leave Epcot via monorail...Note-the Epcot monorail does NOT go directly to hotels...you take the monorail from Epcot to the TTC...then you switch to the resort monorail at the TTC- that will take you from the TTC through the Polynesian, and the next stop is the Grand Floridian. After your meal, take the monorail back to the TTC and then bus to your resort (or monorail back to Epcot if you still have park time left on your schedule.)