Unless the Mission: Space line is super long, I'm not sure the value of going across the park. Epcot can be pretty spread out and Space and Figment are on opposite sides of Future World. Again, this depends on the length of the line. But if might throw off your group if they are in and out of Space while you are still just getting in line for Figment. The post-show area of Mission: Space has a big video game and a few other interactive experiences, and the post-show for Test Track also has some interactive stuff. You might be better off just chilling in the post areas for these, or heading over to Innoventions right next door. All of these are come-and-go, so you don't have obligations to stick around when the rest of your party is finished, and they are also often under appreciated because people are rushing from ride to ride. Once more, it depends on the line that day but with a kid that age you can probably kill at least 45 minutes to an hour checking out the post-show areas alone, and you'll be right there at Mission: Space when the rest of the group is done.