Illusion does not mean haziness, confusion, or mirage. Being a child of illusion means that you continue what you have experienced in your sitting practice [resting in the nature of alaya] into postmeditation experience.

You realize that after sitting practice, you do not have to solidify phenomena. Instead, you can continue your practice and develop some kind of ongoing awareness. If things become heavy and solid, you flash mindfulness and awareness into them. In that way you begin to see that everything is pliable and workable. Your attitude is that the phenomenal world is not evil, that 'they' are not out to get you or kill you. Everything is workable and soothing.
...
It's a very strong phrase, 'child of illusion'. Think of it. Try to be one. You have plenty of opportunities.

From TRAINING THE MIND by Chgyam Trungpa, 1993 by Diana Mukpo.
Published by arrangement with Shambhala Publications, Inc., Boston.