J.V.
I know you would go crazy thinking of the right thing to do.But the answer is DON'T...
SIMPLY--
Dont' get into the middle of things between husband and mom
Don't let yourself get carried away by the criss-cross of tactics the related family brings
If they bring it on as a direct attack to you or your child,then talk to that person directly and do not hold back at that time.End the matter then and there.
Its upto your husband and you to end the matter in whichever fashion you please.If he has taken a decision on what he thinks is best for the family,then respect it and go by it.Similarly if you have decided what to do in a situation that hurts you directly,tell your husband what you decide to do and stick to it.
These are situations in family life which might pass over after sometime but remember children are also affected by the decisions you make and hence choose wisely.
I understand this as I have had similar situations and the best way of dealing with it I realized was face the person ,clear the matter and move-on.Have patience with those who seem persistent.If those people understand that your husband and you are not going to entertain anymore of this drama,they will slowly but surely move away.
Ask God to give you the persevering spirit to know that in time ,things will change...either situations or people's behaviour.Pray for those who hurt you and know that these testing times will bring you to a better place in life.
Hope things work out!God bless.