Actually, no, don’t.
“Say Cheese” is probably the worst thing you can say to a child when taking their photo. It will usually result in something like this photographic masterpiece of my daughter this afternoon (sorry Aimee):
So, if you suggest me to your child’s nursery, pre-school, school, or other care provider, I promise never to utter those two words! I am taking bookings now, so if you would like an information pack for your care provider / school / whatever, please Contact Me and I will send one to you.
(See. I can take nice photos 😛 )