A system of courts and due process is inconvenient and sometimes means the guilty are not punished, but it is preferable to the alternatives.
I've seen no evidence that he was travelling with a targeted individual, or even that the targeting was justified, the statement was I believe 'he was not specifically targeted'. That's because there was no trial, and no evidence presented. Have you seen any evidence, or merely the assurances of gov. officials? Does proximity to a criminal while eating now warrant instant death?
As to the Yemen trial, that applies to Awlaki, not his son, and you have a remarkable faith in the Yemeni justice system. If the US is to assassinate people, I do think they owe them at least a trial in their own courts.
Personally I think this policy is wrongheaded and damaging to US interests in the long term, given all the innocents inevitably killed by drone or missiles in civilian areas. However it's also a sign of declining respect for the law in the US. According to Obama, and yourself if you accept these assassinations, his will is law.