Find and extract the escaped POW
It is best to try and find the escaped prisoner right after you start the mission, or else he may e found by child soldiers and shot. Check out the road Southwards of the village. The initial location of the POW has been shown in the above screenshots but later on, he may go off the road and hide in bushes. It is recommended that you have D-Dog with you, who determines the POWS location from afar.
Extract twelve children
You should try to complete this hidden mission objective while replaying it, i.e. after you have upgraded the fultoning device, thanks to which you can fulton children also (by default, you cannot do this). Still, if you want to complete this mission the first time around, you need to incapacitate children, one-by-one (it is a good idea to use the sleeping pistol) and carry them over to the Southern landing zone (you can do this faster using the jeep in the village).
Find digitalis purpurea
The plant you are looking for is digitalis (purpurea) and it grows on a high hill Westwards of the village. The spot has been marked in the above screenshot.
It may be a bit difficult to climb over the rocks - to do this, you need to reach the North-Eastern slope of the hill. Climb onto successive ledges. After you locate the plant, you need to locate all three specimens, because only after you do this, will you complete this mission objective.