Every country has live entertainment of some sort. A good site to get the current schedule (updated each week but the times don't vary that much when you are making plans) and a description of what the entertainment is all about. There's even links to the group's existing website if they have one. The sets are almost always outdoors so as you stroll around and want to see something, you just stop, watch and if you like, stay or, if it's not your thing, you just leave. No set seating so it's very easy to see the groups without investing a ton of time. Also, with the informal settings, it's perfectly acceptable to nosh on something while you are watching. My husband and I have our favorites but I will refrain from mentioning the ones we enjoy and the ones we don't because each family is different and you can easily see for yourself.
One of the reasons World Showcase is where we end up every late afternoon and evening right there, taking several walks around World Showcase, with an adult beverage in our hand and really taking our time. That's the key to the best World Showcase experience with whatever you decide to do. Take your time. If you get your child the Passport (an excellent idea), let him take his time at the tables. Have him or you talk to the Cast Member.
For me, World Showcase is not a place to have a schedule to stick to.