Yeah, any of the Tales games would be a bit much. (All of them tend to have mature themes) Most of them do have local co-op, so they may be an option. Tales of Symphonia HD releases soon, but some of the themes could be a bit much for their age. I would take a few Tales games for a test run before letting them play. (Beware Graces, it has a rather violent scene early on, if you can avoid them seeing it, it should be ok)
Ni No Kuni was a rare event, aside from some mild language it was kid friendly.
Kingdom Hearts is a safe choice for them, not sure how you could take turns on that one...
The Ratchet and Clank series would also be a solid choice for young kids. The playing as a family part would be a challenge here as well.
Your best bet would be to get a Wii U and play Mario co-op with them. NSMBU and 3D World both have full co-op and Mario Kart and Smash are coming soon, also great family games to play together.