Programmer, Lawyer, Medieval Weapons Expert, Let Them Choose.
When I was 15 years old, my Dad brought home an Apple IIe computer he had bought used from a friend. I convinced my parents to buy a book on BASIC programming and was soon impressing my friends and younger siblings with programs that would print my name on the screen over and over again (by copying the code verbatim from the book). Obviously I was a prodigy. It was not long after that I decided computer programming would be a great job. I could play with computers all the time and make cool games and then play more. I can still remember my Mom's response to my sharing this career revelation with her.
"Larry, computer programmers spend all their time sitting alone in dark rooms typing away at the computer and never see any other people. It is a lonely job. You are so good with people and you will not like it. You should do something where you are dealing with people all the time, like sales or psychology."
What could I say? My Mom was awesome. I knew she loved me and she was always saying that I could do anything I set my mind to. And of course, she was older and wiser than me so if she thought I would be miserable typing away in the dark then I should follow her guidance.
Years later, today actually, I am a successful recruiter, my job is definitely about people, and I truly enjoy what I do. But, I still love sitting at my desk and fiddling with my database, creating scripts to automate tasks, organizing the way the interface looks, linking data. I think I would have enjoyed the computer life. Contrary to my Mom's impressions, programs are not written in isolation. At least not anymore. There is a tremendous amount of collaboration that goes into creating software and a "people person" programmer is extremely valuable.
If we are raising our kids right then they are listening to what we say and maybe even considering our advice. We will have built up a relationship of trust where they believe we actually do have their best interests at heart. Even if they don't show that they understand this all the time. When someone our kids trust and believe in (us, the parents) tells them that they are not suitable for a certain career, chances are they will take that advice seriously. They might give up on it altogether like I did, or still pursue it but with enough self doubt as to make it very difficult to succeed.
Support your kids interests, no matter what that interest may be. Instead of pushing them away from a career that you disagree with or towards one you prefer, help them to make the most of what THEY want to do. If they are intent on becoming a professional soccer player but do not have the talent, help them to investigate related careers like physical therapist or sports agent. Don't just tell them to give up.
Passion for one's job and career is something I rarely see in the workforce today and even with the best intentions it is a shame to take that away from our kids.