Perhaps the Remy's Ratatouille Hide & Squeak scavenger hunt could be an idea? This lets you wander around the World Showcase while the kids have something to do in each country.
As far as touring plans go, I would start with Future World and move on to World Showcase once you've done the attractions you're interested in. If you're relying on Fastpasses to speed things up you could always rope drop Test Track, have a Fastpass for Frozen Ever After around the time you plan to get to World Showcase (plus two other Fastpasses in the morning) and then get 4th Fastpasses for Soarin' as soon as you've tapped in to Frozen. You could then go on Soarin' on your way out of the park (unless you're planning to view IllumiNations, in which case you'd have to double back to Soarin' at some point before then). We've never had a problem getting Soarin' Fastpasses later in the day - in fact we don't bother pre-booking it at all anymore.