Wellesley is a good fund. Also I think diversification is an excellent idea for any of us. Maybe you could include both Wellesley and some index funds. For example you could invest, say, 30% in Wellesley and divide the rest between equity index funds, bond index funds, and cash.
One characteristic of Wellesley is that it throws off a lot of dividends. If you send those to your money market account, that income can be part of what you live on in retirement.
Most of us rebalance at least once a year, which means we buy or sell as necessary to return to our planned asset allocation.
Keep reading! It may seem complex at first but it is so important as you approach retirement. Personally I like this list from the Bogleheads board