[mathking]

I have not hosted a 5K as a robotics fundraiser but have hosted some races as T&F or CC fundraisers. (Before I forget, feel free to PM me with questions.)

Bongle made some good points. These days I will also tell you that some sort of automatic timing system is going to be expected. I think the best thing you can do is see if there is a local running specialty store you might be able to involve. Many of them run road races and can be hired at reasonable rates. They also have a lot of experience with the details. Such stores are also the best place to go for help promoting your race. They will usually let you have signs at the store and will post about the race on their web pages and Facebook pages. Sometimes they will send out information on their email lists. This is the best way to get out the word.

Get your school's cross country involved to help promote the race. If it is out of the HS track and cross country seasons you might try allowing people to run as individuals or as members of teams. You can score the team races by CC scoring or average time or some other method. A team aspect and a summer race can often net you a bunch of high school runners getting ready for their fall season. Those are the kinds of folks who might become regulars, running your race every year.