Seven. For me this is about the time you want to let your kids know that they have complete control over how they look in photos. They can always feel awkward, shy, uncomfortable, But they can make it look they way they want. Confidence is an illusion.
On another point purely technical and photographic. I have a love/hate relationship with this Sigma 50mm F/1.4 DG HSM EX lens. There are times when I take photos and I hate how horribly out of focus it is. It front focuses by more than my canon 6D can correct for and the results are terrible. That said if I do the right thing and take my time. I can't imagine a better lens for taking portraits. Switch to manual focus, rock back and forward a few centimetres, until the eye highlights are in focus and it's perfect in every way. At F/1.4 there is lots of colour shift but the results are completely pleasing.