Your mother and younger brother will be compelled to shun you likely for the rest of their life if not then they in turn could be DF.
You will be considered an apostate and the congregation will hear about your DA exactly as if you were DF "Bebopin is no longer one of Jehovah's Witnesses" meaning you will be lumped together with people who didn't leave for principle that it was no longer the truth. You join, as far as the congregation is concerned, with the ranks of those who displayed criminal conduct, who abuse children, who were fornicators etc.
Apart of me just wants my JW mother to know I don't believe in it anymore. I know if I tell her up front she will go to elders anyway.
What I would do if I was you would be to tell your mother that the Society has a serious pedophile problem and they are pretending that they don't. So over the years there has been a lot of abuse never reported to the police.
Google JWs pedophile problem and read on it. If in researching it you are moved and angered about situation you can convey to your Mom that this issue has created a huge problem for you and you are not happy about this matter and will not consider returning until reforms are in place to keep children safe. Do not discuss anything else with her related to doctrines, flip flops etc.
If she goes to the Elders about it what can they say........ that your wrong........ that there's no evidence. They can't say that and I doubt if they would even approach you about it. Stick with that one issue if anything comes up.
Your Mom will have a hard time disagreeing with you no matter how hard she try's to get you back to the meetings etc.
Of course for others DAing themselves can often be a necessary decision, a strong part of who and what they are and beginning a healing process.
Either way I wish you well.