It's a marathon! How do you keep everyone moving?

We are nearing the end of the second official week of National History Day research and this is what it looks like. My advanced researchers are running ahead of the pack. A few are confident enough to not even look back.
My proficient researchers are leading the pack. They are asking questions and clarifying things. They aren't confident because this is new territory. They don't know the lay of the land in a research project that offers so much freedom. 
I showed a picture like this to my students.  In fact, it was a video and it looked like no one was moving. At the start of the marathon it's hard to see that people are running a race!  But they all MUST finish in the NHD marathon and as the teacher I have to make sure everyone gets just what they need to cross the finish line. 
The task is daunting. I'm a one woman cooling station, hydration station, first aid tent, etc.  This year I've chosen to make a flip video of each day's focus topics. (No more than 2 and and a final thought.) The videos can be reviewed if I go to fast. YouTube even offers closed captioning (not the best but a start!)