We've been wondering/working on boundaries as well. It can be a little sticky at times. So far we've just maintained the status quo; sporadic phone calls, Christmas letters, a picture when I get them done. (I'm not quick with pictures, but all the relatives suffer equally so no one gets to accuse me of favoritism.
) We do have our adopted relative call her bio grandfather 'grandpa'...but we see that side of the family very, very seldom. We keep various bio relatives updated (sporadically) and haven't (so far) made any monumental changes in our family dynamics.
We've been open about familial relationships, and we have more than four adopted children (including non-relative and relative) and each has their own story, so we just have proceeded with our relative adoption in the same manner as we have with the non-relative adoptions. 'This is how you came to our family, and we are so happy....'