The situation is very chaotic at the moment, independent volunteers are allowed to access some of the camps, but not all of them; and the conditions to access change every day. There are rumours that the last open camps are going to be evicted this week, and the people there will be taken to military camps. Things are changing so fast that I have no idea what the situation will be in July. I can recommend several fb pages that update information, like https://www.facebook.com/bienvenidosrefugiadosgrecia/?fref=ts
If I can help you with anything else, please write again!