Hi El Martin,
My advice is that if you meet with an elder you keep it to only one topic....like the UN for instance. I would simply present them with the original documents and ask what they personally think about it.
Keep in mind that a half million JW's accepted the resolution that pointedly stated that members of the United Nations are idolaters and that they are no part of it:
the United Nations, with international headquarters at New York city. This international organization stands for world sovereignty by political men. For years men without faith in God’s kingdom have endeavored to get all people to worship this international image of human political sovereignty as the best hope for earthly peace and security, in fact, the last hope for humanity. To date 111 nations have given worship to this political image by becoming members of it. However, we, as witnesses of the Sovereign God Jehovah, will continue refusing to engage in such idolatrous worship
Since you have already made up your mind about leaving, this is basically for your mother. So, there is no need to get into an extended conversation with them. Just say, Oh, OK, and move on. You can tell your mom that they pretty much minimized your concern.... and that will be the end of it.
Good luck on your next steps after leaving. Will be praying for your success.