i think your analogy is imperfect; if by ordering drone strikes obama is 'deciding to kill children', then by driving a car i am also 'deciding to kill children'. of course i am not making any such decision, rather i accept that one consequence of people being allowed to drive cars is that occasionally a child will be run over, as obama accepts that one consequence of drone strikes is the occasional collateral damage.

it becomes a cost benefit analysis where there is no absolutely good, or right, answer. one simply has to choose what level of risk we are willing to accept.