Planting seeds, to me, starts with the simplest of ideas. Yes, eventually, there are all sorts of classes, videos, hands on projects, even apprenticeships.
But, IMVHO, I think the biggest thing you can do to lay the foundation is to eradicate ‘black box’ mentality from your house. There is so much tech now, for example, that people no longer really take the time to consider ‘how or why’ things function. I think the best thing that you can do is to help kids (and ourselves!) try to develop at least a big picture, working idea of how common things work. For me personally, this means trying to educate myself on things like how exactly the car works, how a computer functions, how to encourage plants to grow, etc.
Then, to always ask the how and why questions with Alex. Usually open-ended so she can try to think it through, and Whatever information I can impart if she seem interested. I really want her to learn to THiNK about the how’s and why’s. I think that developing that sense of interest, curiousity, and ability to think critically will be a big catalyst in learning lots of trades…even if just enough in some areas to avoid being taken in by unethical repair persons 
If you haven’t seen the books by David Macauley like The Way Things Work, The New Way Things Work, etc., we really enjoy them. Fun schematics, interesting topics, great descriptions. I just ordered one about how our bodies work as well. I have these left out in strategic places around the house as I find they get looked at A LOT this way.
I also have found that keeping a big boxes of bits and bobs is a lot of fun. We have one filled with things like old clocks, radios, electronics in one. In another, carpentry items that she can use to ‘make things’.
Another for sewing, and she has already learned to do simple things like reattach a button.
There is a actually a very large, self-sufficient community farm near us that offer all sorts of classes. Things from carpentry to farming to bread-baking, pottery, cheese and butter making, auto maintenance, and every thing you can imagine. As Alex gets older, we plan to do some as a family and some in combos of mommy/daughter or daddy/daughter. I learned some things in the army that I will teach her like block/brick laying, concrete work, welding (although I refuse to teach her underwater or anything to do with demolitions lol )
BUT, I do think the biggest and best sees you can help them plant now is the desire to understand HOW and WHY things work the way they do! Get them to think about it, learn about it, ask questions. Take them on field trips to see people actually doing and enjoying their trades, then have discussions.
And help them to avoid that ‘black box’ mentality above all else:)
) however daddy can’t change a washer so I may need to learn how to do that one myself when the need arises.