Go is honestly probably a better game for what everybody is trying to accomplish here.
I'm actually not trying to accomplish a particular brain-enhancing goal by having my kids play chess. (DD9 plays, too, though not competitively.) They enjoy it, and it seems to be a nice, productive hobby. DS REALLY enjoys it. That's good enough for me. It's great if it has other benefits, though. I'm not sure that I've yet seen any benefits extend to other areas for DS, but I suspect it's helped my DD--the skills it emphasizes are not her strongest (spatial memory/manipulation has never been her strong point, and it's one reason I'm so bad at the game), but she's rather driven to try to keep up with DS.
A downside to chess for our family is that DD is very aware of the lopsided sex ratio in the competitive scene and finds that a turnoff. I keep telling her that this is circular. She's now good enough from playing with DS that she could play on the team and do respectably in her age group (not spectacularly, but I think she would do okay), but she won't because she sees it as a nerdy, competitive boy activity.
