Listen here, love: No child should be in the company of adults who have been drinking!
You need to tell your parents-in-law, preferably with your husband endorsing the statement, that they are welcome when they are sober, but if they turn up having had a drink, even one, you will not let them into the house.
If you go to visit them, having been invited and they are drunk, you will turn right round and go home.
Doing this is hard. My niece did it with both her own mother and her mother-in-law, and her husband backed her up. Her mother finally stopped drinking, her mother-in-law never did, so never saw her grandsons.
Setting boundaries is easiest if your husband agrees with you, if not you have your work cut out to make him see sense.
Probably your in-laws can't stop drinking once they start, and no-one can entirely stop unless they want to. Alcoholism is hard to deal with, but you need to concentrate on your children and leave your adult in-laws to deal with their problem.