Family reunion coming up, first one sense me not being exmormon..

So my first family reunion is comming up and ALL of my family is TBM. I recently have a cousin who is going to recieve his mission call in about 3 weeks here and so i know the question is going to come up about me and what i believe because i've told my immediate family i don't believe (parents and siblings) but everyone else doesn't know. And my family being the gospers they are will spread the news like wildfire.

Now my question is what to do if my cousin who is about the same exact age as me and about to go on mission asks me about what i believe and what to say to him if he does. Should i take my firm stand and tell him everything or basically take it by a little and say "i don't believe anymore because of things i've read about in church history that don't make sense" or something along the lines of that? Have any of you fellow exmormon redditors had any similar experiences to this?

I'd like some help on this subject matter to what to tell family if they ask me why i don't believe. I don't believe because of the book of abraham, inconsistancies in the teachings of the church, Joe smith being a con man, and masonic rituals that are done in the temple ceremony. I mean should i tell my cousin a heads up before he goes into the temple? we were a really close relationship sense we were born beacuse we are only a month apart and i kinda don't know how he will respond to all of this.

Sorry for the ramblings

TL;DR Family reuinon comming up what to tell my TBM when they ask why don't believe anymore and how not to scare them off from being my family members anymore