I actually can't mess this up (except to burn it) so I find it suitable for kids of all ages.....
5oz plain flour
4oz butter (now real butter no fake imitation's)
3oz castor sugar (or normal sugar, put it in a plastic bag and use roller pin to crush it)
Sieve the plain floor, I would suggest melting the butter in the microwave for 5-7 secs, add them together with the sugar. Mix as much as you or your little ones want!
Grab some butter in your hand, run it round a tin, bowl or something suitable for the oven and put it in at 180c/350f for about 20 mins but keep checking on it as it depends on the depth of the tin/bowl etc.
Add raisins or cinnamon or whatever you feel the need to or whatever is FUN too!