Good answer
Standby
In any scenario involving safety - TELL THE PILOT. (if you have time of course!)
there are 2 of them flying the thing and would probably like to be involved in any decision affecting the safety of their aircraft
You can help them make a decision by suggesting what you think is the best option (given the imformation you have) and the pilots can either accept your skill and judgement, or use whatever information they have available to them (do they have enough fuel for a go around? etc etc) to come up with a different option.
One excellent piece of advice I got from an instructor was - if anyone gives you some information, pass it on to someone else because its bound to affect someone somewhere!