I'd focus on encouraging your child to develop strong coping mechanisms.
They don't have to please daddy. They don't have to smile and play Perfect Family Parade in public and then tread on eggshells behind closed doors. They don't have to agree with him about everything. But he may fly into rages if they don't. So they may need strategies to prevent his tantrums and sulks if they show personality in front of him. And they may choose to pick their battles in order to maintain some control over the emotional fallout. Encourage them to understand this is strategic, not giving in.
If he sulks, demonstrate effective behaviour of your own. Stay calm, grey rock, don't dance attendance. If he starts screaming and hurling insults at you or the family, say calmly: I see things differently. I disagree with you and it is okay for us to have different opinions. We are autonomous adults.
Encourage DC to express feelings - especially negative ones – openly to you. Children of narcs are taught only to show happy feelings as narcs can't stand anyone but themselves to have a full set of emotions. An entire childhood of suppression can lead to some pretty neurotic behaviour in adulthood, or a desire to act out like him, since he alone is allowed rages and crying fits and self-pitying monologues. Teach them all feelings are valid and how to express them appropriately not abusively. You can do this when he's not around - maybe at bedtimes or out on walks.
I'd say stuff like: You know dad. It's so important to him that we look like a perfect happy family when we are out. But you know, I don't see the world that way. I think we have lots of feelings for good reason and it's healthy to express them. You know you can always tell me if you are sad or angry or down. No one is perfect and Dad isn't good at coping with negative emotions, but that doesn't mean they are not healthy. Come to me if you have them.
If they are very young you can just ignore any controlling behaviour from him and just say: You seem sad/angry/worried. That's a very normal emotion, you know! Do you know why? What can I do to help you? (Don't say to help you feel better - allow them to have the emotion they have)
Teach them how to self soothe - to find a calm, quiet space to sit with their feelings or to use exercise as a release rather than aggression. To practise self-love if they feel let down or deeply disappointed.
Teach them autonomous thinking. They don't have to be good at sport/music/get A*s/become lawyers/join the family firm etc to deserve love. They are allowed to choose to follow their own path.
If you chat openly about emotional intelligence (no need to call it that), not criticising him but explaining you see things differently, then it will be easier as they get older for them to see through any Disney dad performative parenting and to trust you as the parent who accepts them as they are.