Hi,
PMM aptly answered your concern, and there's no way around it. It appears as if you already know the answers to your own questions.
Unless if you plan on witholding information on your application, which I know you will not do, there's no way your daughter will be considered a dependent after having completed a medical degree, even if she registers now with a vocational school of any kind.
You will not be able to even make a convincing argument that your daughter is making a career change because if a medical student wants a career change, going to a vocational shcool means retrogressing or going backwards. Rather, a medical graduate wanting a career change will attend another graduate program, which sounds progressive.
Remember that Immigration Officers are perpetually trained by their government and they are aware of every immigration ploy there is - so, they will see right through yours - and they will know that you are circumventing or trying to go around the law.
You never said where your daughter is right now, only that your son is in Canada. If your daughter is currently in Canada, she is already fine, as Canada has the International Stream program for international students who graduated from a Canadian university and would like to become PRs.
Even if your daughter is out of Canada, she is still fine because you can still apply without her name under the dependents section, but you can still fill in her name under members of your family because she is.
And then, when you land in Canada in the future, you can always sponsor your daughter.
I can understand where you are coming from, but look on the bright side, when you land in Canada, your daughter will one day land also, through your sponsorship.
You will all be fine; just go through the required process and exercise some patience.
Warm regards,
Libra.
