Elizabeth has it right...
I'd add only that someone who self-identifies as a a non-practicing Jew or secular Jew still isn't any thing else (ie Christian). It is one thing to not go to synagogue -- it's another to go to church. Lots of these folks mark religious occasions by having big family meals -- they just leave the G-d part out.
Because your Jewish heritage is actually even further back than your parents, you can say your ancestors were Jewish (and to be more accurate you might want to clarify by saying "Russian Jews" or "German Jews").
BTW, I believe that confirmation is a relatively new stage, done in part to encourage Jewish teenagers to continue learning instead of stopping at the bar or bat mitzvah stage. The choice to continue being Jewish isn't a declaration per se, I was never bat mitzvahed (although merely turning 12 was considered good enough) or asked to declare my continuing intention to be a practicing Jew. I just continued to practice by attending synagogue voluntarily, lighting the Sabbath candles and not eating pork.