My parents are very religious muslims, so it wasn't even a topic that was open for discussion as tattoos are so forbidden in Islam.
My older sister got a tattoo before me, and whilst i knew my parents hated it i was never around to see my parents finding out about it so i had no real idea about what sort of reaction they had. So i got my first tattoo on my back, second on my chest, and then my third on my forearm. During healing i was wearing a long shirt to hide it, and i kept bringing up the "Can i get a tattoo" and my mum would always say no, i brought it up once when i was in my mums room and whilst talking about it, she spotted the gap i had in my shirt (It had buttons down the sleeves kinda thing) and demanded to see my arm, she freaked out had a nervous breakdown, sent me out of her room, cried for a couple of hours and i could tell it was easily one of the most upsetting things in her entire life. This same ordeal happened (And to this day does) everytime i'd get a new tattoo and she'd "Find out" about it. I have a full sleeve now, entire chest and other tattoos here and there, and it's still something that plagues her, she can't stand my tattoos. The point is, even if your parents are only a little bit opposed to it, or completely opposed to it like my parents, showing them sooner than later is the only way to go. When i'm hiding tattoos i have this constant fear of them seeing them, and when they do know all about my tattoos at least i have a sense of relief.