If you can find a calm time when you can talk sensibly together and privately, then perhaps you could discuss things in a better manner. You may have always had some differences in how you perceive their behaviour depending on your own backgrounds, but perhaps are both retired and find it harder than previously to cope with long spells with the children, especially if you did not altogether agree with their behaviour in the first place. The starting point would seem to be to think how their parents expect them to behave, and not accept anything less from them when they are with you.
Then you might discuss where your personal limits of behaviour when you are out in public are, and perhaps if you think the children are deliberately antagonising him, seeing it as some sort of game to see who can annoy him the most, you need to put a stop to it. So in my case when they next talk about going out for a meal, you calmly say that they do not behave well in public so for now you wont be going out, but will eat at home. If they improve a little, you might consider a take away occasionally, but certainly I think that you and your husband need to present a united front. It will not help them at all to think that poor behaviour is acceptable, whether young or old, and you do not want to end up with a you plus grandchildren against your husband, where he will feel that you are being disloyal, and ganging up on him and whilst his language on that occasion was not good, your grandchildren will grow up and go their own ways, and if you have upset and antagonised your husband this may lead on to further problems instead of being able to enjoy each others company.
I think it would be a useful thing to be a bit observant and see if you notice changes in your husband, sleeping less well, eating a lot more or a lot less and then go on from there to find out if ther are underlying problems that he has not mentioned about his own health. If you are in a lot of pain or not sleeping you are much more likely to get snappy and upset than if you are sleeping well. I would not think it disloyal to ask perhaps other adult family members if they have seen a change recently, as it is possible as you se him every day that you might not notice it in the same way. Hope that you find something that helps