On one hand, I guess that it is nice that she feels sufficiently attached to your son to feel that he is an important part of her life and wants to include him. On the other hand, I personally wouldn't like to broadcast pictures of my children on the internet. I think that I would go carefully here, you don't want to spoil the relationship that she has obviously developed with your son, but at the same time you need to make sure that they are aware of your feelings about posting his picture and why.