hey- just wanted to share that i've been going through similar stresses. I'm 26, been getting tattooed since i was 22. my mom really hates them, my dad doesn't seem to mind too much.
my solution has been to just not show them when we are visiting (this isn't hard for me to do, as i haven't gone below the elbow yet. i can conceal everything with long pants and a t shirt.)
i get stressed out about it at lot, and sometimes i feel guilty about how my mother might react if she knew about each new tattoo i get. but that fades. and really, even despite all the great things your parents have given to your life, it's your body and your choice. life can be a trying pain in the ass, and if tattooing is something that helps you stay enthusiastic, then just do it because it really isn't hurting anybody.