So, my family says i'm being mean to my daughter! ?

hello, I have a 3 month old little girl. my family adores her but we have a situation. my sister has a 15 month old son. my sister Kayla does not care what mason eats. honestly this kid eats cheetos, soda, goes down for a nap with sippy cups full of juice constantly, he has been eating twinkies and other little debbies since he was four months old, and he is always eating. my parents was watching Mason today and i went down to visit. while i was there for an HOUR he ate a lunchable, bunch of crackers, some chili and also had juice and soda, all in an hour. i have tried to educate her on nutrition but she could care less so i have just come to the realization that i can dissaprove until the cows come home, nothing is going to change so i just don't bother. so my family is allowed to be so leniant with him they think it is ok to do it with my daughter. the problem is is that i have been stressing to my family that my daughter Piper will eat healthy, organic food. (i am not implying that people who do not feed their children organic are bad, it is just what i prefer. i say as long as its a balanced healthy meal, your doing your job) everytime the issue comes my family says im being mean o her and that what i don't know wont hurt me. like i said, my family adores her so i dont want to keep her away from her papa and nana but i want my decisions to be respected. how do i resolve this once and for all without taking drastic measures. right now my mom and dad watch her while my bf and i are at work. we were thinking of putting her in daycare but my mom hated the idea and really wanted to watch her and i feel good with everything else besides the nutrition thing. i don't want to put her in a facility were she is just another crying baby to them! please help!