Innoventions is something that we pretty much skipped the first couple of times we took our kids, and I never really felt like we missed much. We have since made it a point to explore a bit more, just to see what we had been missing, and our kids actually enjoy going in there...but if we skipped it again, I seriously doubt they would miss it.
There are some scientific experiment sort of things....a banking game (built around a piggy bank...your six-year old would enjoy it)...a create-your-own-coaster area/Sum of All Thrills (check the age/height requirement on that, but if tall enough, I would imagine your six-year old might also have a good time creating her own ride and then riding it in the simulator). There are some video games (not sure of their purpose other than to let parents rest!) and a fake house that has something to do with fire safety.
If I have missed anything that is really great, I would love for another poster to let me know. Right now, it's mainly a place where we go to get our "free" Disney Visa cardholder photo made.
In summary (and in my personal/humble opinion), Innoventions is one of the prime examples of the continuing decline of Future World in EPCOT. Hoping that the Imagineer recently tapped to put EPCOT back in the direction of its original intent can get in there and do some good things relatively soon.