Rent the Goodyear blimp and put 3 guys with IR scopes on board. Nighttime would work best.
************************
Just a couple of Bell helicopters with IR at night would do fine. I saw video from our test stands years ago that showed a motorist about 1 1/2 miles away who had pulled off the road to take a leak. The man and his ‘stream’ were clearly visible on the video.
You can hear the Helos from a mile or more away, plus they have only a 2 or 3 hour endurance. The blimp can just sit up there, engines giving just enough thrust to maintain position.