First, I believe the simple answer is: Yes, it can be proper.
One of the teachings of the Noble Eightfold Path is “Right Livelyhood”. In this teaching the Buddha laid out the requirements for a job to be helpful to moving forward toward enlightenment – even for non-monks.
As long as the encouragement to follow their interests includes teachings on how to recognize a Right Livelyhood I would say such encouragement would be quite proper.
As to the specific issue of ‘Attachment’ in this:
Most lay persons need to have a job / livelyhood to live. To my way of thinking, just because one finds a job one enjoys and has an affinity for, does not imply they must also have an exaggerated or unhealthy attachment to that job which would hinder their spiritual development.
Again, if the parent or teacher imparts teachings of how to recognize symptoms of unhealthy attachment to things of this world and of the proper perspective as to what a job is, in the wholeness of a person’s spiritual existence; again, I would say such encouragement would be proper.