I think it's hard being as young as you are because it matters so much more what the family thinks. If it weren't for that I'd say who cares what they think but in this case, I guess you do have to consider them.
That being said, they
are being judgemental. Lee said it quite well about college not being for everyone. I'll use myself as an example. I am a federal employee. The kicker is, I do not have a degree which is rare in my field. I am in IT doing programming and database development and taught/learned everything on my own or on the job. There are people in my field with degrees and know less than I do. I do not say that as a boast, but as an example that it does not automatically make you successful with a degree or vice versa. I worked hard to get where I am. So yeah, a degree isn't necessary.
The other thing is, I have very high respect for those that are very skilled in a trade whether it's electric, plumbing, machining or agriculture to name a few. The thing is these people actually can work much harder to reach the top than the average college worker that gets his job from a piece of paper. What that says to me, is that skilled workers are many times more dedicated to the work thy end up in simply for the fact it takes them years to get to where they are and it's not just scores on tests. They also have to love their work more because they have to learn their job by doing, more so than a college person taking all these courses that will never be used.
That's just my 2c.
What to do? try your best to talk to your family and I agree, they should get to know him better. I think that they are looking only at the surface, the book's cover, so-to-speak and they need to really dig in and learn the whole story about this guy. But to speak on their side, they are only thinking of your future even if he is just a high school bf right now. They want to see their child end up with someone they think will take care of her.

They just need to recognize his trade choice as being potentially very lucrative.
Hope this helps. *hugs*