The key word, I feel, is "goal." That's what separates a vision from a mission.
For example, think of the old-fashioned and stereotypical mission, with white Christian missionaries who travel to deepest, darkest Africa to save the benighted savages. The missionaries' vision (or goal) is to convert an entire tribe from animism to Christianity.
Their mission, on the other hand, might be to learn the tribe's language and then communicate the Christian message to the tribe's members in their own heart language. Providing them with a Bible in their heart language might also become a method of strengthening or reinforcing the spoken Christian message. rnjai's answer in this regard is good: Vision is the goal; mission is how to achieve the goal.
By the way, a more common approach to religion-based missions today is to seek entry into a tribe's culture primarily by 1) coming to understand and respect the tribe's culture and values; and 2) "earning the right" to be heard by, for example, helping an illiterate tribe achieve literacy, or setting up a clinic where sick tribal members can be treated at no- or low cost. Only after "earning the right to be heard," do the missionaries then present the Christian message. In other words, demonstration of the love of God comes first; proclamation of the love of God comes second. Obviously, both missions are inseparable.