Tearaway Unfolded and Little Big Planet 3 are good ones! :)

Rayman Legends might be too hard, but its kid friendly.

The one and only Knack, my friend!

Tearaway is perfect and out in 3 days.
Lbp too

Knack, for sure. Not sure why there's so much hate for it. It was a perfectly good game, which i thoroughly enjoyed. One of the few games i own for PS4, that i've played through more than once. And no, i'm not a child, i'm almost 40.

Let them try Flower. Any of the Lego games.

Yep, Knack should be an automatic "get" in this case. Two buttons and two sticks, pretty easy to pick up, and the production values are high enough (and loud enough) that kids will want to. 2p is there to ease a child into it, and there's plenty of side things to do to keep them playing well after the campaign is finished. And if they persist to figure out how to deal with the higher difficulty settings, you've now got a full-fledged core gamer on your hands.

minecraft knack and littlebigplanet are for everyone

That is one way to look at it, the old school way. I grew up like that and kids can overcome the challenge if they really enjoy gaming but Knack is going to be really tough as a starting point. Then again, I did not think this through....

You are 100% right. I have not played co-op ever in Knack so I completely ignored it.

There arent. The ps4 is a machine created to be played only by vikings. Adult vikings who have hairy chests and enjoy rude and mature videogames to be precise. If you want games for children go play nintendo, that thing is for babies without a single trace of hair on their bodies.