I say na-DEEN, but if I met someone who said nay-deen I'd probably adjust to that pronounciation quickly.
It sounds very heavy because of the two n's IMO, but I think it would suit any age. I think it's quite glamorous, but without being too showy.
And no, I don't see it as dated :)
I think it would work best with something N-free:
Julia NadineNadine JuliaIris NadineLydia NadineNadine Eloise Nadine AloisiaNadine JosephaGabrielle NadineNadine LauraNadine OpheliaSarah NadineNadine SarahMatilda NadineNadine MatildaNadine ScarlettNadine GeorgiaGeorgia NadineFelicity NadineNadine Lisette :)
Like any?