I'm a bit late.
Sounds like it could be fun, but I would have everyone on horses. Great way to show off all of the different horses and steeds that people have, but as you said I'd probably have them walk part of the way at least.
You could vary it. When in population centers (e.g. most of the Shire, Bree-town) you could have the procession walk through, but then in other areas where there aren't people (e.g. Trollshaws) you could move at a faster pace. Perhaps even a couple of mini events within the event along the way.
Definitely get the word out though. And then don't listen to the nay-sayers (which unfortunately FF has a few loud ones) Let them go on with their boring old lives and let those who want to have some fun join you. If it's a time I can be there I'd love to come along.
Firefoot: Elendale (hunter) Galorlas (champ) Grimlaff (warden) Corny (warg)