11 and 10, and as for making them smile, the older one is way more relaxed, but more internally nervous. The younger one is intense, in everything - you should see when they fight.
Of course, you should've seen the first take - after I showed it to them, the younger one decided to smile at the end.
And thanks for the comments on YouTube guys - they really got a kick out of it (especially after their cousin Imi got some).