I am so sorry that he cannot step back just a little. He does not realize he is going to drive his children away. They are going to begin dreading having to with him.. His loss.
To teach children manners, everyone in the home must use them at all times with each other. Does he say yes mam and no sir to your children every time? How about when he speaks with you? If not, this may be something you all will want to concentrate on. This way it is a natural habit for ALL of you.
Children respond better to positive reinforcement than forced behavior. Each time they remember on their own, your husband will be better served if he will say. "I liked your manners just then." Or 'thank you for remembering to use your manners with the waitress."
Once again have a heart to heart with him and let him know how really upsetting this is to you and you have not enjoyed a meal out or travel in years, because his behavior makes you nervous.
Also if you are really uncomfortable, let him know you feel the pleasure of going out is now lost for you. It makes you sad, but it is just not something you want to participate in if he continues this way.
Ask him of a different way he could respond.. The other thing you could do is somehow record these situations with your camera. Do not let him know you are going to do this, just let it happen organically. Once he sees and or hears that everyone was having a good time till these incidents occur, he may realize what a damper he puts on the family,.