The DS1820's are very good. A little care would be needed for such long cable runs, but project should be do-able.Do you need absolute temperatures, or realtive? (Precision or accuracy)
Readings per minute?
Number of sensor?
In a warmer room at 18°C, the candle measures 27°C at 2 meters. This is because the candle only occupies a small part of the sensors field of view and the candles point heat source isadded to the back ground ambient - not swamped by it. A human at 2 meters will show up as around 29°C with a background 20°C ambient.
They (thermopile) have a very wide detection angle or field of view (FOV) of around 100° and need either shrouding or a lens or commonly both to get a more useful FOV of around 12°.