DS actually likes both. He collects the SOTMK cards- which means we start a game, play a portal each time we are in MK, and finish one adventure each trip. You must play a portal in order to get the new set of cards. This does not take up a lot of time, but we still play and get cards, which is half the fun! We usually get new cards at the firehouse on Main Street, but I believe there are other locations to get them as well.
Agent P we can usually finish a mission (barring technical issues with the phones or the game elements) in about 20 minutes. The mission takes place in one country and you can pick it. There are several kiosks around WS where you can pick up a phone- and you drop it off as the last part of the mission. This is interactive with the phone/directions from the characters on Phineas and Ferb, so you finish the mission in one session.
Neither of these takes up an immense amount of time, and are fun to try once or twice. There is also a pirate adventure game in Adventureland that is similar if they are more into pirates. Again, one mission takes about 20 minutes to complete and has an interactive map. You could do this one a step at a time as well- just keep track of where you stop on the map (note where it told you to go for the next clue so you can go there when you return).
Hope you have fun trying one of them!
