I buy a new game every year or so to play with my siblings, sister-in-law, and now my nieces (exact same ages as your girls) when we're all together at Christmas and other times during the year. I was looking at a lot of reviews last week and settled on
Anomia. I think a lot of your decision will hinge on your younger daughter's abilities.
If you want to try more of a light Eurogame vs the traditional family/party game, the 11-year-old absolutely loves
Ticket to Ride and
Pandemic and is actually pretty good at them. She wants/tries to play Settlers of Catan with us but it isn't a great fit just yet; she understands the rules and can play with some logic but isn't quite there yet in terms of strategy.
I'm in my mid-forties and we still play
Can't Stop. That and
Survive (also recommended) are the only two games that have "survived" 30 years of my mother's purgings. I think Survive is back in print (or was a few years ago) so it might be easier to find. We also play a lot of
Heads Up, which is a phone app, and
Scattergories, although for that I just printed out a bunch of lists I found online vs buying the actual game.
There have been several game threads like this over the years if you need more ideas. The Dice Tower channel on
youtube has a ton of different reviews covering different genres.
http://www.dicetower.com/game-video/12-games-christmas-2015-family-games