I have played all three Lego games that exist to this day on the Wii console (Lego Star Wars, Batman and Indiana Jones) with my 6-years old daughter. These are all very good and fun games to play. The controls are easy to understand, the characters are funny, the gameplay is very easy without being boring; these are the perfect video games for an adult to play with a younger children.
The reason why I prefer Lego Indiana Jones over the other two is that this game puts more focus on solving puzzles (and the other two games were already good in that aspect). To move on in the game, you will have to find the right tools and perform the right actions, which often require a lot of collaboration between the two players. It's not all about fighting the bad guys.