1. You have to make it fun. It should be about laughing and having fun, like you're at a party but it's a running party. Make them want to be at that running party.
2. Who cares if they like some guy on YouTube? How about "Hey we're doing this plyo workout and here's run_strong_coach demonstrating how to do it". Everything in your program is probably somewhere out there on YouTube being explained by someone else because unless you're Jack Daniels or Arthur Lydiard your program is probably based on someone else's work. So go find the videos yourself and text it to them. Then they'll be showing your videos to other people instead of showing you videos. If they show you one that isn't part of your program: "Oh man, that guy's a clown", then show them another video explaining why. Don't try to make them believe in you, make them believe in the training. Then when they get the results, they will believe in you because you found them training on the magic internet that actually works.