In regards to World Showcase at Epcot, my DS4 is usually more than happy to trundle about with us. We usually use our time there to relax and not rush about from one attraction to the next. He loves the outdoor trainset in Germany and will spend as long as possible watching it go round. We usually take a few eating breaks as we walk round (particularly if it's the Food & Wine festival) and my son is happy to play with his toy cars on the bench while he waits for us. Germany has a nice little toy shop that sells more toy cars, so he can't wait to get to Germany, and Japan also has some very interesting little toys in the big shop there. So if we forget to bring something with us we can usually find something small to occupy him. He loves to drive round the world, as Mummy & Daddy are eating around the world! We try and get him to say hello to a CM in each country in their language, he likes to do that in Japan best, as he always gets a great response from the ladies!!! I don't think we have ever taken him into or on any of the actual attractions in World Showcase, and he still loves it. We have never needed to use the kidcot stations, or the passport which is great as we have those in reserve if he ever does start to complain! The characters and street performers in these areas are excellent too. So much going on visually that he really is perfectly happy. You can get some excellent photos of the kids outside each of the countries, they are my favorites in my scrapbook.
Hope you have an awesome vacation.