Meet and greet and attendee management for a walk event

We are running a sponsored walking event on Sunday 28th November, with celebrity/influencers in attendance, and a group of around 30-40 members of the public who are supporting the charity. The walk has been promoted as unguided, but we'd like an Event Manager on site to represent the charity, meet and greet, circulate, and support the walkers and celebrities. The start and meeting point is the Decathlon store on Kensington High St, walkers have been asked to arrive from 06:45, for the walk to start at 07:15. The walk is likely to take people around 60 minutes, returning to the same point.