"And Jesus came and spoke to them saying, 'All authority has been given to Me in heaven and on earth. Go, therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, [even] to the end of the age.'" (Matthew 28:18-20, NKJV)
A mission statement is a formal, yet short written statement of the purpose of a company or an organization. The mission statement guides the actions and activities of the organization by delineating the immediate goal of the company or organization which serves to govern the decision-making process of the organization. "It (mission statement) provides the framework or context within which the company's strategies are formulated." 
Historically the mission statement, according to the Online Etymology Dictionary, was associated with Christian or religious groups. The OED gives the example that a "missionary" was assumed to be a person a specific religious mission. 
What is the mission of the Church? What statement, while formal and short, serves as the purpose, or reason for the existence of the Church? Does the Church need a mission statement?
Second, let me also say that the over-arching mission of any individual and church is to glorify God. Our duty or responsibility as believers and churches is to make known the magnificent, glorious, and marvelous character of the living God. (Isaiah 46, I Corinthians 10:31)
Third, let me say, that God has chosen to glorify Himself, or to magnify and make know His glorious character by redeeming a company of believers, adopting them as His own, indwelling them by means of the Holy Spirit, gifting them with a spiritual gift, and charging them to make known His character to the entire world, i. e. every tongue, tribe, nation, and peoples.
Initially God revealed His glorious character of Himself to Adam and Eve. After the fall, He made His character known through anthropomorphic expressions of Himself in a pre-incarnate form. He chose to reveal His nature and character through the nation of Israel. In keeping with His eternal decrees and secret purposes, God continues to reveal His glorious character throughout the Church which began on the Day of Pentecost.
The church has a holy calling and responsibility of revealing the nature and character of the living God to every tribe, every tongue or language group, and every nation on this earth. I do not see anywhere in the Scriptures, either Old or New Testaments that state that this holy calling and mission requires that the good news of the gospel and/or God's glorious character be revealed to every living human being. God has never stated that He intended to reveal Himself to every living human being, but to people "..out of every tribe and tongue and people and nation..." (Revelation 5:9)
What then, is the mission statement for the Church? What statement, derived from Scripture governs the purpose and reason for the existence of the Church which is represented visibly and locally by individual and local churches? What becomes the filter through which every decision, plan, program, goal, or ministry is governed by? We call it the "Great Commission." We find it in the last paragraph of Matthew 28.
Each local and individual church is charged with the responsibility of making disciples. Notice this is the main verb in this paragraph. "Go" is not the main verb. Go is a participle or supporting verb. The main verb tells us that our commission is to make disciples, the participles or supporting verbs going, baptizing, and teaching tell us what is entailed in making disciples. The word "Go" is not a command or call for a few people called "missionaries" to go, it is a participle that actually says "going, "or "as you are going," "while you are going" - make disciples. In your everyday life, as you conduct business, raise a family, build a home, develop a career, recreate...make disciples.
What are we told in Matthew 28? The mission of the church is to make disciples. The Holy Spirit opens the heart of a lost individual when the gospel is preached and regenerates a repentant sinner. This newly saved individual is baptized. Then, the work of discipleship continues! The church is told to teach these new believers to τηρεω (tay-reh’-o), "to keep, to preserve, to hold fast to, or to observe" all the things that Jesus taught. This is dicipleship. Evangelism or sharing the gospel is only part of the entire equation.
There is nothing wrong with being a friendly, fast growing, welcoming, homey, hip, and whatever local church as long as the mission is not replaced by this desire. I would want people to think of the church that I shared leadership in was friendly and outgoing. I, also, want them to know that the over-arching thrust of our church is to make disciples. Families within our churches extend and give longevity to their blood-lines by having children. They raise these children in order to one day raise children of their own. Churches perpetuate their spiritual longevity by continuing to make disciples.
Look back to some of the greatest churches in history - the Jerusalem Church, the Church in Antioch, the Ephesian Church, where are they? Gone. Why? They left their first love and when they did they failed to continue to adhere to their mission statement. In other words, they failed to continue to make disciples. Your church may be 20 minutes old, 200 years old, or anywhere in between, but if it doesn't adhere to the mission statement in Matthew 28:18-20, it will eventually spiritually peak, and then begin to decay and die. In some cases a mere shell exists because someone refuses to give up and shut the door.
What is the written mission statement of your local church that serves as a filter or governor of every decision, program, or goal decided by the leadership?
 ^ Hill, Ch., Jones, G. Strategic Management. Houghton Mifflin Company: New York, 2008. ISBN: 978-0-618-89469-7, page 11
 ^ http://www.etymonline.com/index.php?term=mission