Hey there, Jeannette! Welcome back to the Disney Parks Moms Panel.
I'm so glad you stopped by with your question today. Planning how to use your FastPass+ selections is like putting together a big puzzle. It helps to have an idea of what your final picture will look like before you start.
If you know you want to take advantage of morning Extra Magic Hours, do be aware that there are no FastPass+ selections available during that time. I'd get to the Magic Kingdom entrance before opening (you should be able to catch the welcome show before Extra Magic Hours, too) and hop on some of the more popular attractions before the bulk of the crowds arrive. You can try to ride Seven Dwarfs Mine Train first thing, but this may also be a good time to hit the other super popular attractions like Peter Pan's Flight or the Mountain rides (Splash Mountain, Big Thunder Mountain Railroad, Space Mountain) when they're not so busy. Then, I'd save those precious FastPass+ attractions for later in the morning or afternoon when the standby waits for those rides are longest. You can maximize the number of attractions you're able to get in this way - or maybe even use it for an extra turn with those elusive dwarfs!
I hope this helps, Jeannette. Please come visit us again if you have any more questions while you're planning your practically perfect Walt Disney World vacation!
Keep Disney Dreaming,
Kathy K.