The Pikmin game in NintendoLand, while similar to the mainline Pikmin 3 game, plays a bit differently than the actual game. Assuming your son plays as Olimar (on gamepad) in the NintendoLand game, I would think he might enjoy the actual Pikmin 3 game. In terms of difficulty, there are some parts that can be tricky but there's a pretty soft "time limit" on the game in that you have to average about a fruit collected a day to avoid running out of time. Outside of that it's a pretty relaxed game if you want it to be and it's a blast building up a massive army of Pikmin (much more than the small amount you get in the Nintendoland game). The only thing I could see making it slightly more confusing than the Nintendoland game is the whole 'managing three captains' aspect of the game and the fact that it is much more open in terms of level design than the linear levels in Nintendoland, although you can get by through a lot of parts without doing anything overtly complex with that until the very late stages of the game.