As a general rule of thumb the best day of the week to visit EPCOT typically tends to be Monday, Tuesday or Wednesday. We would recommend visiting on a Wednesday during the festivals mentioned above.
Can you do EPCOT in half a day?
EPCOT is arguably the least family-friendly park at Walt Disney World, so you may not need more than a few hours to do everything of interest if you have small children. With that said, a full day at EPCOT is highly recommended for first-timers.