VWAHX looks risky for money needed in three years. VWITX isn't bad but the SEC yield is only 1.53%, in exchange for some interest rate and credit risk.
In contrast, a 3-year CD with Discover Bank will get you 1.2% APY, basically risk-free (0.9% after your taxes). If I were you I'd probably put what I had already saved into 3-year CDs, assuming you're pretty sure you won't want the money before then.
I've been learning recently about how the bond market's past returns have been pretty good the last few years but that's about to dry up as all the 5- and 6-year notes issued before the financial crisis come to maturity. This is why recent yields on bonds have been so good but SEC yields are so low. CDs are now a better deal than bonds (they actually have been for a couple years now). thefinancebuff.com has been covering this in several blog posts.