Five options, not three
Don't know the veracity of the story, because of course most films take some artistic and dramatic licence, but in the film they discussed.
1. Slotting them
2. Tying them up
3. Letting them go
4. Of course it remains that they could have taken them with them. They had cable ties to restrain them and restrict their mobility. Cables ties are very versatile and you can restrain or immobilise people in a number of ways to prevent them escaping or resisting you. You wouldn't have to take them all the way with you, because it's a two way trip. They have to get back and warn the militants, then the militants need to travel back to the area. Taking them for two or three hours would be a two or three hour trip and then two or three hours of travel time for the militants. If your movement time is pretty constant, each hour you took them along would buy you two hours.
5. They could even have tied them all together with the cable ties in such a way that they could only have made their way back to the village at an absolute snails pace, such as lashing their ankles to one another one facing forwards and one facing backwards, etc. with three people you could tie them all together at the ankles all facing inwards, like a triangle or tie wrists to ankles, etc.
Like I said, don't know the real story, but the dilemma as shown in the film felt a little contrived.
"Yeeha, just like f%^cking Saigon eh slick"?
"I was in junior high dickhead"!