Hi Rachelle! Welcome to the Disney Parks Moms Panel!
I don't have experience with E-Tickets but I have purchased Military passes from my base and they sound similar. Both allow the purchaser to link their tickets to a My Disney Experience profile and make
FastPast+ reservations in advance, but the purchaser also has to validate the passes in person once they get to Walt Disney World Resort.
In my experience only Guest Relations windows can process these tickets. I've twice validated our passes the morning we visited our first park, and another time we processed them at the
Guest Relations desk at Disney Springs the day before. It really is a painless process that takes about five to ten minutes, plus however long your wait in the initial line to get to the window. If you're trying to "rope drop" a particular park, or take part in morning
Extra Magic Hours, I would absolutely recommend validating your tickets the day before so you're good to go for your first day of fun.
I hope this helped, Rachelle, and we'll see you real soon!
~Kristen