Hello Amanda and welcome to the Disney Parks Moms Panel!
IllumiNations: Reflections of Earth is by far my favorite nighttime spectacular at the Walt Disney World Resort! We never miss it. While there are a few areas around World Showcase Lagoon where you might be able to sit while enjoying the show, they are very challenging to acquire as they are very popular. One such location is the terrace adjacent to La Cantina de San Angel. If you are willing to secure your seat 90 - 120 minutes before the show begins, this is a great location. However, if you are willing to stand, there are many great vantage points to see the show without the need to "camp out." Simply look for a place on the rail that isn't obstructed by trees and where you can see most of the central part of the Lagoon.
With that said, my favorite all time view of IllumiNations: Reflections of Earth is from one of the
Specialty Cruises. While not inexpensive, these cruises not only provide an amazing view of the show, they also give your family some quality time on a relaxing and fun pontoon ride through Crescent Lake. And, you are guaranteed a seat!
If you have more planning questions, don't hesitate to come back to the Disney Parks Moms Panel!
See ya real soon!
Anne