Interesting. I've only known a handful of interfaith couples, and none of the children identify with being Jewish. This, despite all the attempts of Liberal/Reform temples to embrace such families.
Its a tradition not to evangelize among Jews so I don't know that the Reform folks are really doing all that much to reach out, but alot of the kids I know from mixed families are finding their own ways back. Some in Messianic groups, others Orthodox, and some back to Reform temples.
Funniest thing, cause if you ask them they will say its something they never planned.
These are not twenty somethings, but instead adults, 30's, 40's and 50's.