MapRunF has a risk waiver
on their Event Terms and Conditions page, which you should probably request all participants to sign.
As far as a safety plan goes, course setting should be responsible and avoid dangerous areas, and any such areas should be described in the event information.
Provide a safety bearing (xxx degrees to xxx major feature).
Advise participants to take water and emergency supplies, and dress appropriately for the anticipated weather conditions.
Provide emergency phone numbers (police, ambulance, fire, rescue).
My club is doing none of these - our MapRun events are all short courses in urban areas. But then here in the Covid-free capital of the world, we're able to run normal orienteering events.