You're not winning if there's that many participants...guaranteed that several of them are ready and trained for it.
When you move your legs to run, you are mostly using the thigh to move the leg. But the distance you cover per stride is determined by your feet. A lot of people, especially when they sprint, use very quick thigh movements, but very small steps, which is completely wasting all the energy used to move your legs. Which is why a lot of fast runners have nice long strides, simply because you cover a lot more ground per leg movement. So when you are running, do not have your calves and feet lagging behind your knee, every time you take a step consciouly move your feet slightly further until you reach a comfortable stride. And if you aren't used to running distances, don't go too slowly at the start, because odds are the pain you'll be feeling by 2 or 2.5 km will be the same regardless how you started (but of course don't go too quickly). Take a good solid pace, but DO NOT DEVIATE from it. Even if your mind thinks 'Damn I need to slow down' remind yourself you are already at a solid pace, and any slower would soon result in you jogging. Keep up the pace.
by thigh im assuming you mean quadriceps which isnt where your power comes from all quad does is move your leg forward after the kick. hamstrings is where all the power comes from. aside from that your post is pretty on point but can be summed up in a few words. maintain a long stride.
Power comes from the glutes, mainly. Its important to note he shouldn't try to reach/lead with his foot. He'll excessively heel strike and probably pull a hamstring.
