Since your mission statement is only a few pages long, your executive summary will allow you to further expand upon key points mentioned in the mission statement. Consider including your business history, biographies of key players, an overview of the business including locations, employees and available products and services. You can also discuss goals and future plans. Use this section to really draw in the readers.
On average, a good business plan will be about 15 to 20 pages. Keep it concise but detailed. A good business plan will pay dividends both in the short and long terms. An investor and/or bank manager will see this and if the plan holds up well, then this will bring you the business that you seek. And from a personal point of view, a great business plan is something that you can return to time and again as a good reference point - something that you can draw upon in the future.