You can encorporate as a for profit organization or a 4013(b) not for profit. Numerous legal websites can tell you which forms you'll need to encorporate based on your needs.
Most states require incorporation to be written by an attorney. Check with other school organizations and see how they handled it. Ask if there is a lawyer among the members.
The IRS has information specific to writing these articles for booster clubs. You can consult their website, or call your IRS office, believe it or not they are very helpful!
