Hi, Dara!
Great question!
The most popular opening ceremony in Walt Disney World is the
Magic Kingdom Welcome Show which takes place at park open. One family is selected to join the fun as Mickey, Minnie and their friends arrive on the Walt Disney World Railroad at the Main Street, U.S.A. and greet park Guests with song, dance and celebration. It's a great way to start the day at Magic Kingdom.
IF you are going to Magic Kingdom early in the morning, then be sure to get there in time to see the ceremony. (I'm the type who hates to miss an opportunity by just a few minutes; might as well add one more experience to your list, right?)
Similarly, there is an opening ceremony at Disney's Animal Kingdom Park as well, also including characters and music, where Mickey and Minnie welcome all of their friends to the park for the day.
There are several Guest videos of these ceremonies posted on YouTube; take a look to see what's in store and then decide if this is something you'd like to see in person.
In short, we try to see an opening ceremony on days when we're heading to that park at park open anyway. It's a nice little addition to start the day magically, but we don't get out of bed early and race to a park just to see the show.
Keep in mind that there will be lots of Guests lined up to see the show as well, so arrive earlier than 10 minutes before showtime if you'd like to be up front. Once the ceremony is finished, know which attraction you'd like to enjoy first and head in that direction. You'll be among the first to enjoy it that day and will have plenty of time to wander throughout the rest of the park in the gorgeous morning hours.
Happy planning, Dara! Send more questions as you think of them; we love to help!