There is a long list of target retirement funds that own Vanguard stock and bond index funds at a very low cost of .08%. Simply select the fund that fits your desired asset allocation (70% stocks vs. 30% bonds and cash for example). You can type in to the search engine at Vanguard to identify how each portfolio is broken down based on the number that is attached to the fund. As always, factor in other money within your portfolio and the spouses, if applicable, when making this very important decision.
The Target Retirement Income Fund (VTINX) could be used as a low risk savings account during times of very low interest rates. The funds asset allocation does not change from the 70% bond (includes about 17% in TIPS) / 30% stock allocation while you invest there. One would consider using this fund when they are willing to take a small amount of stock market risk to try to get some kind of return that is hard to come by with cash and even bonds when interest rates are ;very low. This fund could be used as a all in one fund for the retiree who prefers simplicity.
Here is another way to look at target date funds. You can pick one with low fees and simply feed it as much as possible until you are ready to retire as it rebalances itself each year with a higher bond allocation as you appoach the year on the fund. In the early years, you will have a 90% stock allocation to U.S. and International stocks. When you hit the number on the fund, you will have about a 50% allocation to stocks. When you reach 3 years after that number, you will stop at 30% in stocks and that is where it stays while you own that fund.