I'm taking over as organizer of an annual sponsored dog walk in a small town. It has been well supported in the past (usually about 40 dogs and their owners) and is for a great animal charity, but the walk is usually just a 1km stroll around a park which always feels like an anticlimax!

I'm thinking about organizing a second route that would be more like a three hour hike on a wide trail to get a more adventurous type of dog owner involved, and hopefully raise more sponsorship.
Any tips for how to ensure that lots of dogs together doesn't turn into chaos?