I think you’re on the right track. Manipulation is overriding someone’s will in service of your motives. Persuasion is offering new information, while respecting their autonomy to make their own choice. So you are right that intention matters a lot. And the reason it matters is that your commitment to their wellbeing is an investment in the relationship which is a mutual interaction over time not a single event.

That’s also why authenticity and honesty matter. If you lie to your children or spouse or colleague they might do what you want one time but over time not trust you. If you are inauthentic they will also learn that you have ulterior motives and become distrustful.

The last thing I’ll say is it’s not always a negotiation. With young kids or direct reports there is elevation in the relationship, meaning one person gets to make the decision and the other gets to follow the instructions. So when a toddler is saying I don’t want to brush my teeth if you treat it like a negotiation you actually make them less secure about their place in the world because they aren’t ready to make every decision for themself. One good technique I learned is to simply present two choices. “You can brush your teeth or let me brush your teeth”. That’s very different than “let’s go brush your teeth” which can be answered yes or no. So it’s not always necessary to engage in persuasion. Sometimes framing is all you need.