Can 7-9 year olds play Rock Band / Guitar Hero? I've played those a few times and they seem pretty fun.
I've tried a little with my 6 year old, but I think he's a little too young for it. I bet if I let him play more...he'd be better. It could be worth it with your kids Dave.
I find the Lego games always fun Matt, and a lot of replay value... While I don't like it, Battlefront is a fairly tame shooter game. Titanfall I love and consider it a little less violent too since it's got robots and stuff. Shooters may be a little too advanced for the youngest though. My gf's kids did ok with them though at that age but that was a long time ago.
Hell, I bought an X-box one back in July and other than Halo5...I've just been replaying Mass Effect!