Jambo, Karen!
Welcome to the Disney Parks Moms Panel! One of the reasons why I love Walt Disney World Resort is because I can leave the transportation logistics to someone else!
The fastest and most direct way between Disney's Animal Kingdom Lodge and Disney's Grand Floridian Resort & Spa would be a
Minnie Van, which is an app-based ride hailing service. An additional charge, a Disney Cast Member provides door-to-door transport for up to six guests, and even includes the use of two car seats.
If wanting to use
Disney's Complimentary Resort Transportation, the most direct way from A to B is to catch a bus bound for Magic Kingdom Park, and to walk on the sidewalk between the drop off and Disney's Grand Floridian Resort & Spa. It's about a 15 minute walk, and the path is near the Monorail entrance.
If you have a bit more time to leisurely enjoy your journey to dinner, you can take the same Magic Kingdom Park bus, but hop on the Resort Loop Monorail instead of walk. The Grand will be the fourth stop on monorail, which would add about 30-40 minutes to your travel time.
Another way to add a bit of transportation whimsy is to take the same original bus to Magic Kingdom Park, but then use a complimentary Water Taxi. These will be located between where the bus drops you off and the monorail entrance. I would add in another 30-40 minutes for this service, too.
Lastly, you technically can take a bus to any Disney Theme Park or Disney Springs, to then catch a bus bound for Disney's Grand Floridian. But I would only do this as a last resort as you would still incur a wait to catch the second bus.
I hope this helped, Karen, and We'll See You Real Soon!
~Kristen