Photos Without Reflection In Specs

I really struggle sometimes to get photos of the kids without reflections in their glasses so I was happy to get this one yesterday at the park







In contrast to the best of a bad bunch on Friday when he was dressed up for a school trip back in time




Any advice on how to stop the reflection is very welcome.

First picture was with hipstamatic on my phone and the second was with my camera. First one was mid afternoon and second was about 830am with no sun. Obviously he has created his own sun block on the first with his arm but any further advice would be fab.