What game to choose for a family with 8-10 year old kids?

It really depends on what your kids actually like to play - action games, puzzles, adventures, or something more relaxed. From universal options, I'd recommend the Rayman series (bright, fun platformers), It Takes Two if you have a console (it's specifically designed for family co-op), or classic puzzles like Portal 2 and Portal. Another good option is Switch Sports if you have a Nintendo - there are lots of games for the whole family there.