My son loved the Passport at that age, and was able to appreciate it in a way he could not when he was younger. You can find them anywhere in WS (as you know), and they're a wonderful opportunity to meet and speak with some of the international Cast Members who are so kind and so eager to tell guests about their homeland. Perhaps your son can use it (as mine did) to open conversations with the CM's that he may not have been 'ready' for when he was a bit younger.
For instance, my son (now 13) still remembers how to say Please and Thank You in French, Mandrin, Chinese, Japanese, Spanish, German and Norwegin, all of which he learned in Epcot's WS, having generated conversations from their signing his Passport.
We have also slowly aquired some of the 'traditional' items (such as the pickle ornament in Germany, which is proudly hidden in our Christmas tree each year) from each country, which is another lovely way for an 'older' child to comemorate his or her visit to the countries.
I'm sure it goes without saying, but trying things like the Kaki Gori, Rice Cream, etc, in each country is a big hit and something my son looks forward to each visit. There is so much at Epcot worth exploring with our 'older' kids, and I'm sure others will come up with ideas to make WS a true family experience for kids who are just a bit past the character autographs and the masks.