Vivian is nice, perhaps a tad old-fashioned but there's nothing wrong with that. What I'd be much more likely to use is the French
Vivienne which I love (the way it looks, the 'enne' ending which I'd pronounce). I don't think you can go wrong with either. I'm sure you'll get plenty of combos so I won't bother, but I'll say that my stock
Vivienne combo is
Vivienne Claire which is so sweet (and so French).
BTW, I'm not as crazy about the
Vivien and especially
Vivianne spellings. The former seems masculine to me while the latter doesn't look as proper as
Vivian or
Vivienne.
Also, if you feel
Vivian might be too old-fashioned, might you consider
Viviana?