I think that it's a good move. We had decades, nay centuries of violence between Britain and Ireland, if you read Irish history it's a miracle that he would be seen at Buck House himself. If you remember how the conflict with Ireland was resolved it came about when we were too thin on the ground militarily with conflicts starting in Iraq and Afganistan so the diplomats sat down at a table with the Irish and did a deal. This is how all wars are stopped, not on the whole with bombs and bullets but with words.
Maybe the Mullahs from Afganistan and Pakistan should be invited as well. The Queen would have the respect of them as a real royal personage rather than the jumped up temporary war god wannabes like Obama and Camoron.