Unlike a large organization with committees, a small group will have to throw the various tasks onto the table and see who wants to handle them. Most often, a person will take on the tasks she feels most confident performing. Each person needs to make a personal pledge to do the job because there is no formal structure, no board members, and no bylaws. In this kind of situation, everyone holds each other accountable for the responsibilities they pledge to take on. Failure to do a task can strain relationships and friendships.
If someone does a job as they see fit, everyone should either accept the outcome or politely make suggestions on how to improve it. This can be a touchy area. It is important to make and accept critiques in the spirit of achieving a greater good. Critiques shouldn't undermine another member, or you risk compromising your entire mission. Planning is important, but each person should agree not to make any unilateral decisions.
While you may turn the money you raise over to a qualified 501(c)(3) charity, you cannot advertise donations are tax deductible because you yourself are not officially a nonprofit organization. Nonetheless, you should provide individuals with a statement of receipt for their records that says you sold them an item or provided a service.
While many tasks will be divided, everyone will be involved in the overall job of raising funds though selling, performing a service, or asking for money. Carefully determine your plan of action and decide where you will each be soliciting funds. If you are soliciting for contributions, you do not want all participants contacting the same people. Similarly, if you are selling candy bars, divide the territory, decide where the group will convene, and who will collect and be responsible for depositing the money.