I did find this page for the 2/5.... watch it for a while to make sure it is legit... See if they keep OPSEC....
https://www.facebook.com/groups/2.5marines/

Someone mentioned doing a search with your son's unit on Facebook. Iknow that my page I created for my son's unit was secret, so it wouldn't show up on a search... you had to know someone who would invite you.... So there may be a Facebook group that just doesn't show up.

Jennifer,
My son is part of 2/4. They were leaving the same area as your son was arriving. I was able to connect with a lot of parents through Marine Parents, and then I created a secret Facebook page with some of those parents.
I will pray for your son. I know that they have hard work ahead of them but with prayers they will get through it!
This was my son's first deployment so any information or picture of anyone or anything were highly valued.
The phones were down during the end of their deployment so their were no pone calls. He didn't Skype at all either... Facebook messaging was short and sweet, but at least I knew he was somewhere safe if he could use the internet.  
He said one of the the things he most enjoyed were letters from elementary school kids. I would recommend that if you have any connection to schools to get them to send letters as soon as possible..... Memorial Day would fit well into a curriculum for them to write letters. He treasured those letters.
My son LOVED the bread that he would get the ANA or ANP to go into town to get for him and he said the chicken was the best. I would send in single dollar bills in his boxes and that is what he said he spent his money on. He LOVED the Afghan food!
If you have any questions, please feel free to contact me!