Hi Kelly,
Thank you so much for visiting the Disney Parks Moms Panel with your question. It sounds like you have a fun day planned - starting at Disney's Animal Kingdom and then heading to Epcot for the Disney Vacation Club Merry Member Mixer!
The Merry Member Mixer looks like so much fun - it includes character meetings, holiday crafts for the children, and a dance party. More information about the Merry Member Mixer is available at the
Disney Vacation Member Website. Once you have logged in, scroll down and you will find a link to information on the right. From this information, I see that there is a Merry Member Mixer listed on December 15, but not December 13, so please do double check the date that you plan to go.
I suggest that you plan to be at the bus stop at Disney's Animal Kingdom about an hour before you want to be at the Merry Member Mixer. There are
buses that connect Disney's Animal Kingdom to the other three Walt Disney World theme parks, so you should be able to catch a bus directly to Epcot. Leaving an hour will give you time to wait for the bus, and then to walk to World Showplace, which is located between the United Kingdom and Canada pavilions, once you arrive at Epcot.
As to whether you need to arrive immediately at 3:00 p.m., I think it will be okay if you are not there exactly on time; however, do note that the Merry Member Mixer runs from 3:00 p.m. - 5:00 p.m., so you probably do not want to arrive too late in order to be able to take in all the magic!
Have a great time planning your vacation, Kelly, and please do not hesitate to ask if you have any further questions.