Personally, I think it would be better to teach your new students in person. It allows them to see what they're learning first hand, right in front of them, and it makes it much easier for them to ask questions, or bounce around new ideas.
Those types of videos would be very useful for rookie teams though! Or even other FRC teams who may just not know how to use a particular machine tool, or work with a certain component.
Now, if I were on a rookie team, I would probably want:
- Building a basic drivetrain
- Pros and cons of various common drive systems (Belts vs. Chains, Kit frame vs. custom, number of wheels, etc)
- Explanations of electronic components (how they work, what they are used for, differences between various motors, etc)
- Building, wiring, and setting up a basic electronics board
- Building a basic pneumatic circuit