I've been gaming with my sons since the earliest days of 3e. We started with the minis game, which worked great for teaching simple math, and BlankBoy1 (the oldest, now age 11) loved it. But BlankBoy2 (now 9) wanted actual role play, so I introduced them to the Basic Set for 3e, and moved on from there. We have gamed off and on ever since, eventually including BlankBoy3 (now 7). They have fallen into roles, with the oldest playing tanks, the youngest spellcasters and the middle son likes rangers, or anyone good with a bow.
When I first started gaming with them, I asked Gary Gygax for suggestions in one of his (now lost) threads here on ENW. His response has been in my sig ever since.
We kicked off Father's Day weekend this Friday with our first Castles & Crusades game. We had played a couple sessions of 4e, and although I like it I felt I needed something simpler, so I converted their PCs and they jumped in willingly. It was one of our best sessions ever, and the PCs are making their way towards Blacktooth Ridge, the first series of modules for C&C.
I did convert one aspect of 4e: I've been running an NPC cleric to provide healing and some guidance, but I've decided they are ready to be on their own. With only three players, and none of them interested in a decicated healer, I developed a simplified version of healing surges. Each PC gets 3 healing surges per day, and each surge is equal to half their max HP.
To top if off, they (along with WifeBlank) got me three more C&C modules for Father's Day, so we are set for some time. I took the BlankBoys to our FLGS for Free RPG Day and bought them each a new set of dice. We finished the weekend with a spirited game of Munchkin last night.