For me, I am running ActionTiles on 2 Tablets and 2 phones as of right now for the $23.99.
As for having multiple children, some of the flexibility you have is creating multiple panels for what devices each kid can see, access and have as a functional tile (pincode required), and preventing them from being able to access the administration console. One kid, you might only want to be able to access lights and one kid can arm / disarm the system and lock / unlock doors, so they would have different panels / shortcuts that each of them would access.
The one thing I’m most impressed about is what ActionTiles started as at the beginning of the year, and the number of enhancements that have been implemented since then and where it is at now. I can access all my devices, view my cameras, receive voice notifications on my tablets (not an AT feature), have real time weather maps displayed, auto wake up of the tablets when I walk by (wall mounted not AT functionality). I rarely use the SmartThings Mobile application.
Smart Home Monitor Tile access after entering 4 digit PIN