Tried it with my 5yo daughter. Several sessions so far. The game tottaly does everything it's up to. It's very easy to pick and to explain, but it's flexible and it can deal with any situation or your kid's idea. And the book is short (which is good for me)

To create a character you ask the player what their PC can do. Settle the names for those (my daughter first said 'command', but changed her mind in favor of a broader 'be a queen') Then ask the player, what is PC best at? Repeat 3 more times.

The roll mechanics is easy. Each ability assigned a dice (d12, d10, d8, d6). The player rolls it - 2- means a failure, 3+ means a success (we used a slightly advanced mechanics)

K.I.S.S. principle at its finest

Also the book holds a bunch of good advice on the subject and some great adventure seeds. I love it