I am the adoptive mother of a 12yr old boy (he was 4 when he left his family, 6 when I met him and 8 when I adopted him). Because he was a foster child the state would not allow contact with his biological family. Now that he is adopted it is up to me until he turns 18 then up to him. I have tried to facilitate him having a continuing relationship with his biological family. It has been difficult for everyone (but well worth it IMO). I have tried to allow his biological family to set the pace as they had already mourned his "loss" having been told they would never see or hear from him again. From my sons perspective things are moving too slow.
It is a dance like the start of any "new" relationship. I think they take on a life of their own. Put yourself out there as you feel comfortable and give him the space to respond as he is comfortable. If he has made the effort to find you then having a relationship is important to him so it is only a matter of timing not an "if".
Remember to keep breathing.
I think having FB and/or email is a nice option to have in the early stages. Each of you can open things when you are ready to see them and send things any time.
Good luck!