If you want a PV angle to this, how about getting "PV Teams" to enter the 5K race. Not sure how many per team, but the whole team must hold onto the pole the entire race, crossing the finish line together. Of course, get sponsors for the teams.
Another variation that works better around a track than in a 5K road race is that one team member drops off and is replaced by a new team member on each lap.
I'm not aware of this ever being tried anywhere, but maybe add/drop a team member after each 1K? Just an idea. Whatever you can do to create interest and make it fun. Maybe encourage the teams to dress up in funny costumes, and award a prize for best costumes.
Kirk