I need some tattoo advice could anyone help me?

Yes I'm 16 years old I will turn 17 soon i've been thinking about getting a tattoo for a little over 2 months now I Have no clue on how to approach my grandparents and I know that typical 16 year old males just want tattoo's to say they have them but I haven't ever been as sure as I am about wanting this tattoo. My great grandfather recently died and due to the swine flu infection no1 under the age of 18 was allowed to see him. He was the best grandfather a kid could ever ask for. Whenever I was down or feeling slightly bad I would walk next door to see him and we would sit in his kitchen for hours and tell eachother stories from our lives. See the thing is I miss him so much and I never got to tell him that I loved him before he died. The last time i saw him was 2 weeks before he went to the hospital. So, in my mind I've been thinking what I would like for rememberance and that is a cross on my chest with his nickname (Poppy) and the world love inside of the cross. Now i don't want this tattoo to be visible because I know from experience that it's extremely hard to get a job once you have gotten tattoo's in areas that are visible to employers thats why I've decided to put it on my chest. See waking up every morning and walking into my bathroom looking into the mirror and seeing his name on my chest will not only help me get through the rest of my Highschool years without him since he was the one and only person that kept me motivated. I waited and thought about this for a long time and it is truly something that I want on my body for the rest of my life. To me it's kinda like keeping him close to my heart as a symbol of my appreciation for Poppy. I need advice because I'm scared to approach his daughter my grandmother and tell her that I know im still young but I've given it alot of thought and this is what I want. So could anyone please give me some advice?