How can I prevent my son from being hurt ?

I used to be married to Gertrude . Gertrude and I are divorced and we have an eleven -- year -- old son, Ben . It looks like I’ll have to go for a restraining order against Gertrude . Gertrude is hardly the best mother in the world, and I have the idea to have Child Protective Services investigate Gertrude . Ben thinks Gertrude and I are friends . I’ll admit Gertrude really has tried to be friendly, but there’s too much bad blood and resentment for ue to have a good friendship . I’ve talked about the restraining order and the CPS investigation with a few friends, but I haven’t mentioned it to Gertrude or Ben, so they don’t know anything about it . Ben doesn't realize our divorce is such a powder keg . If I go for a restraining order or involve child services, it'd come as a BIG SURPRISE to Ben and his feelings could be hurt ! How can I explain the situation to Ben ?