I am so sorry to hear this. maybe they are just trying to prevent your mother and your abuser from having access to your kids during the holidays.

heres something that worked for a friend of mine... make plans where you are not going to be around your mother where you can have the children... ie plan a supervised picnic, plan a supervised meeting place other than your mothers place or where your mother could show up.

When I was a child I was removed from my parents household while my parents and social services prosecuted my abusers. in order to have visitation with me my parents could not see me in any situation where I may accidentally or on purpose run into my abusers and those that allowed the abuse to happen. my parents instead of meeting me in that town and popular hang outs of the abusers and their friends planned things like picnics in other towns, a trip to the zoo, a shopping trip, all kinds of visits where I could still see them but not come in contact with the abusers.

maybe those that wont give you contact because of possible coming into contact with your mother can help you plan a visit somewhere some place where your mother cant be around.