I love roleplaying games, and I love playing games with my kids. Putting the two together is not an unobvious thing to do.
My kids can deal with pretty complex games, but they are still young and so a full-on system is overkill on so many levels. There are existing roleplaying systems for kids, but the one I have looked at most closely is both tied to fantasy settings, and apparently owes much of its structure to Dungeons & Dragons.
I do not care for D&D.
My solution to this was to use a system derived from a different roleplaying system called Savage Worlds. This is the system that we are more or less exclusively using in my roleplaying group, and I like it a lot because it is setting-neutral, the core mechanics are simple to learn, and it plays pretty fast. It is still too complex in its full form for the boys to deal with just yet though, so I trimmed it a bit: cut the number of skills, especially, and simplified character creation. In fact, I wrote up characters based on the boys’ ideas.
I ran a short superhero game session, and the boys loved it. We used LEGO minifigs as miniatures, and they battled an alien dragon that emerged from a tunnel and had a blast.
The next outing is to run a game for a group of kids we know – I’m going to use the same basic version of Savage Worlds, but my thinking at this point is to run a story set in Middle Earth. This is a setting I will have to do very little to explain, since there has been so much Hobbit and LotR exposure over the last decade. It is also a low magic setting – one of the difficulties with the superhero game was that the superpowers were a bit complex to run. If I am running a game with 6-10 munchkins, I want this to be as simple to follow as possible.
Besides, I want this to be about story and character and puzzle-solving rather than combat. Combat always ends up more complicated than you expect, and it’s easy for an encounter with even a handful of characters to get bogged down in minutiae.
I will post details of the game system itself when I have them properly written down. I may even post the game materials once the game is played.