I think everyone is over thinking this announcement. Say he was born in Kenya, not sure any of the Dunhams or Obamas are thinking of citizenship. How about just proud parents or grandparents announcing a birth. The announcement does not seem to be an official record of birth that appear in some newspapers.
Given the Leftie nature of the Dunhams, the ability of their grandson to avoid the draft by just going to Kenya for a couple of years must have occurred to them.