As much as I'm a HUGE fan of Wellington and Wellesley (and own both within a much broader and highly diversified portfolio), neither fund gives you broad exposure to the equity markets as each holds < 100 stocks - total. More specifically, Wellesley holds 68 and Wellington holds 93 as of the latest reporting.
Assuming you're looking for broader diversification, either VTSAX (Total Market) or VINIX (S&P500 index) + optionally VEXAX (Extended Market) if you also want broader Mid and Small-Cap exposure would be good choices. If you'd like, you can hold Wellesley/Wellington and these other funds - I just wouldn't recommend all of your eggs in the VWINX/VWELX basket..
I just read a great article the other day on Seeking Alpha that studied the performance of a combination of Wellesley, Wellington and a S&P500 index fund. Wellesley provided the "ballast" (worst year was < -10%) while Wellington was more conservative than a pure stock fund (having ~35% bonds). The S&P fund then gave the growth - if you could live with the potential 50+% drawdowns along the way. Backtesting this gave some pretty solid results as Wellesley and Wellington provide some bond exposure (albeit, with a heavy tilt toward corporates and less Treasuries than would be ideal) while the stock components of the 3 funds provide upside during market rallies. If you really want/need Treasuries also, adding VBTLX (Total Bond) or a pure Treasury fund like VFIUX would do that..
ETA - as great a fund as Wellington is, there have been periods of extended drawdowns that you need to be aware of..I don't have the data at hand at the moment, but if memory serves me right, the worst was ~3 years underwater. Of course, that beats the heck out of the S&P - for example, starting back in 2008. Wellesley predictably given it's greater bond holdings was less (~18 months IIRC)..
Hope that helps! Good luck in whatever you decide to do.