I've been thinking about becoming a guide. Lots of hoops to jump through first. Business license, Marine Merchant License from the Coast Guard, first aid and cpr classes, 1 million dollars of liability insurance. All before ODFW (or maybe it's the state of Oregon) gives you your license to guide. I'm sure I'm forgetting something. I only skimmed the requirements since it'll be quite a while before I'm ready to take the plunge. So don't quote me on this stuff. Seems like your "I'm technically not a guide, but I do accept donations for consumables", might not be a bad way to go.
Depending on how far out you go and what you're targeting, ~$100 a head seems reasonable.