Another short post:
I learned a very simple rule years ago about giving advice, whether to friends, relatives or children. It is amazingly simple, incredibly effective, and really hard to stick to. The rule is:
Get permission before giving advice or offering suggestions.
My experience, and the reports I get from the people I have shared this with, is that when we have permission to give advice then we are much more likely to be listened to. And if we are not given permission then by graciously keeping quiet we avoid wasting a lot of energy and annoying the listener.
This is a very hard rule to follow so the damage-control rule is:
If you gave advice without permission, apologize.
Regarding when to start doing this with children. Once when my daughter was 3 she was having difficulty putting her shoes on. I asked her if she wanted some help and she replied “I do it myself!!”