Your FP selections are solid. You should definitely try to see Soarin. You can try doing it at Rope Drop or employing some strategy you find on the boards, but you can just do it the old fashioned way by getting on the standby line. Ditto for Frozen Ever After.
Probably like most people, we work our way through Future World then head into the Worldcase. Beyond the FPs you have and Soarin, you also have Mission Space, which I believe your older child can do. There are two attractions in the Imagination pavilion, one on short films and the other is a ride with a "Figment" of your imagination. You have two attractions in the Seas pavilion, Nemo and Crush Turtle Talk, which is adorable. My family has spent hours in aquarium part of the Seas after doing these two things.
Also in FW are Living with the Land, which is in the same building as Soarin, and Ellen's Energy Adventure, which I like to do in the late afternoon so I can take a rest.
Several of the World Showcase pavilions have movies or rides. Mexico and Norway have boat rides (Frozen Ever After), and China, France and Canada have movies. The American Adventure has a movie with animatrons. You can also find entertainment in each country that will be listed in your times guide.
Honestly, everything I've listed more than fills a day between walking between things, actually doing them, snack breaks, and looking at all the decor and exhibits. My family has never found it boring no matter how old the kids were.
Take some time to explore whatever strikes your children's fancy. That could be the aquarium. Or it could be the exhibits inside Mexico or China. They may be fascinated by one of the gardens in Japan, France or the UK. There's a great train display in Germany. And the department store in Japan is great (Pokemon).
Just go and enjoy. It's an amazing place with plenty to do, see and experience for all ages.