This app was mentioned in 2 comments, with an average of 2.00 upvotes
This is cute and the 5 year old could probably use it: https://play.google.com/store/apps/details?id=com.blippar.cardio (requires simple gaze interaction)
I showed this to a 2 year old - seemed to love it: https://play.google.com/store/apps/details?id=com.warprecords.squarepusherstoreiglass - (no interaction required, just look around and enjoy the crazy stuff)
(and if they like the Squarepusher experience, they might like this too: https://play.google.com/store/apps/details?id=com.MindTravel.DubWorldFREE )
Direct link to Googleplay store (no registration required)