I have been on the
Family Magic Tour twice. We enjoyed it very much, but it is really geared for younger children, not teens. This two hour tour through the Magic Kingdom takes the form of a treasure hunt. The mission of hunt changes from time to time, but when we took the tour, the goal was to find Captain Hook's missing hook.
There was a big map with clues that kids and parents took turns reading from. There was a tiny bit of Disney trivia knowledge that came in handy, but this was really not necessary. Mostly the hunt could be completed by doing silly things in the parks like walking backward through Tomorrowland or "hiding" from an animated character in a restaurant. During the tour, the guide will often, but not always, take the group into a ride or two, allowing you to bypass the line. The grand finale of the tour comes when the group solves the mystery or completes the hunt and a character comes to congratulate you. For example, when our group found Hook's hook, Peter Pan came out to talk with the children. I have to say that this was by far the best character experience we have ever had in the parks (and we have had a lot of character time). Peter Pan spent about 25 minutes with a group of six children that happened to be on the tour that day. He spoke with them individually for several minutes and then played games like "Duck, Duck, Goose" with the entire group. Depending of the size of your individual tour, there might not be quite this much personal interaction, but for us it was amazing.
So ... your four-year-old would probably have a great time. (Bear in mind that there is a fair amount of walking on the tour, so you might want to keep the stroller handy just in case he gets tired.) But other than watching their brother have fun, this might not be so entertaining for teenagers. To make a reservation for this, or any Disney tour, call 407-WDW-TOUR.