Hello Amy! Welcome to the Disney Parks Moms Panel.
One of my favorite tips to Guests going to Walt Disney World Resort is to figure out how to incorporate the International Gateway into their vacation. Whether a visit to
Disney's Boardwalk or as a shortcut to World Showcase, it is seldom busy and a pathway for Endlessly Magical Epcot Experiences.
I may be wrong, but I believe the breakfast buffet at
Disney's Beach Club Resort you are referring to is
Minnie’s Beach Bash Breakfast at Cape May Cafe. Your plan to drive to Disney's Beach Club Resort and enter Epcot through the International Gateway is solid, however Parking at Walt Disney World Resort Hotels for
Advanced Dining Reservations is limited to a 4-hour window and leaving your vehicle parked all day is frowned upon and monitored by security.
If you are booking your Advanced Dining Reservations after has Epcot opened for the day, you could always park at Epcot and walk through the Theme Park and through the International Gateway to Disney's Beach Club Resort. That would put your car where you needed it after your day at Epcot.
For the experience you described, I would drive to Disney's Beach Club Resort for breakfast and then park at Epcot after my meal.
Try to set aside some time to stroll down Disney's Boardwalk. It is an often overlooked experience by Guests and a unique Disney experience.
Bon Appétit!
~Todd