It is up to you whether you want to ask if the charity benefitting from the walk will meet these. Depending on the type of walk, people may well need a map and directions. This could tell people such things as the route, points of interest, toilets and refreshment facilities along the route, and what to do at the end, You can either give this to people on the day, or you can send it out in advance in which case of course you would also tell people such things as where the start is and when to arrive. You are likely to need copyright permission if you propose to photocopy a published map. However, you may be able to get permission free if it is for charity.
Media Do a press release and tell the media what is happening.
It may help in creating interest to point out that the walk is one of a series happening around the world and is part of International Stuttering Awareness Day. Acknowledge people Thank people for taking part. Maybe give people a certificate for completing the walk. Collecting the money This should be done primarily by the participants from their own sponsors. Support people in collecting the money from their sponsors.