Good family games...
All the Lego games are fantastic. They can be played solo, or co-operative 2 player. The games feature platforming, simple combat, and puzzles that will often require both players to work together. Lego Harry Potter is great for HP fans, Lego Marvel is great for Marvel fans...there's quite a few choices. There's also Lego Worlds which is like a creative building game where you can build entire worlds of Lego, make vehicles, build and furnish a house, complete quests etc. It's good fun.
You've probably heard of Minecraft? You can play 4-player on the PS4 and on top of the building stuff there's a selection of competitive 'mini games' that have now become the main draw for my kids.
Rocket League is fantastic and can be played up to 4 players at home. Football but in cars is the best way to describe it.
Rayman Legends is another really fun platforming game that up to 4 people can play at once.
Another option is a Nintendo Switch? They're a bit more expensive than a PS4 but you'll get to play most of what I listed above plus Nintendo games which are really family friendly.
Mario Kart 8 is a bright and colourful kart racer, plus you can turn on steering assists for younger players so they have a chance of winning. Splatoon is a shooter...but family friendly! You have paint guns and the main goal is to cover the level with your paint colour. There's also 1,2 Switch which is a collection of daft little motion control minigames that you'd all be able to join in with on Christmas Day.