I don't think videos are going to be part of this. They are already spending way too much time in front of a screen, so I find the hands-on approach preferable. We have natural ponds, ocean, puddles on our street, and a few houses nearby have ponds (to teach filtration), so mini field trips to look and gather stuff will be so much better. Plus, we are not afraid of getting wet, after all, it is the Pacific Northwest and we are well acquainted with Wellies.
I like the simple beginnings of
@Colin_T 's suggestion. My challenge is getting sunlight since we will be starting in January and we can go weeks without seeing the sun. My daughter teaches food chemistry to high school kids, so we are brainstorming ways to introduce the nitrogen cycle by observing it in nature. Like trees breathe air which contains nitrogen, but they can't "eat it" that way, so they need the roots to absorb the nitrogen that gets prepared for them by the bacteria in the soil... you get the idea. Comparing jars with nutrient rich pond water and plain tap water and observe growth of duckweed... Anyway, lots to do.
This is going to be lots of fun, I can't wait!!!