It makes me so nervous whenever other people have my child in the car with them. How do I know they…

It makes me so nervous whenever other people have my child in the car with them. How do I know they have his seatbelt straps tight enough, the chest clip on his CHEST, and the car seat as tight and safe as it could possibly be?! I am a perfectionist and a worry wort, so every single time we go anywhere I will sit there forever making sure everything is adjusted properly because I couldn't risk something happening even if we are just going 5 minutes down the road. My mom especially worries me because sometimes she just seems a little off. How can I nicely say I need to check how you have the car seat installed and adjusted before you go anywhere? She is SO easily offended and if I say anything she will freak. I just wish she could handle constructive criticism without being so defensive.