Given your party, and the fact that the youngest is seven, I doubt that you will have any problem doing the Magic Kingdom in one day, especially since you will be there on an evening Extra Magic Hours day. And your meal reservations have been made.
If I were you, I would sit down with a park map and mark those attractions I wanted to visit. Then I'd plan a route through the park, keeping my meal reservations in mind. In planning your early morning, keep in mind the fact that the Jungle Cruise won't open until one hour after park opening, and probably won't be running during the EMH time.
The last time I visited the Magic Kingdom during evening EMH (Sunday, March 19), I made sure to do those things I really wanted to do BEFORE the regular park closing time (such as the Carousel of Progress and the Tomorrowland Transit Authority for example), leaving other attractions (such as Splash Mountain and the Haunted Mansion for example), for the late evening times when many of the crowd would be long gone.
You could plan one circut through the park beginning after breakfast, doing the attractions that will not be open during the EMH time. And then plan another trip through the park doing the big things that had huge lines during the day, but will not be crowded as you move into later EMH times.
You should have plenty of time to do it all. I hope y'all have a great time.
Enjoy.