I think the Passport would be great for older kids, but for younger ones I'd suggest just doing the FREE mask. DD almost 5 loved making the mask- they stamp the handle at each country and add a different charm. With the passport the CMs would write an entry and it took FOREVER. We went during a somewhat busy week and some of our longest lines were to just get our mask stamped because those passports took sooooo long to fill out. (We didn't have a passport, we just had to wait for everyone else...)
If your kid doesn't have genuine interest in the passport entries and/or is too impatient to wait for them to be filled out I'd skip it until they're older.