Beam down to the largest settlement.

The concerns of your junior officers are legitimate, but in the end the need to respond to a distress call takes precedence. That does not mean you can't take precautions, though. Mr. Spock locates a landing site in an open field where an ambush is unlikely, but within easy walking distance of the largest settlement. You also instruct Dr. McCoy to inject subcutaneous transponders into the landing party -- they've proven useful in the past.