Some schools have simply eliminated all fund-raisers on a trial basis and have solicited direct donations instead. Instead, contact parents directly. Make all volunteers feel welcome and appreciated. Make sure all have specific responsibilities and introduce them to other parents. Don't overbook your volunteers.
People volunteer their time when they feel they are really needed.
Make sure your fund-raising activity is legal. Be sure you understand your individual state laws before you have a raffle or a casino night. Check insurance before hosting a sporting event. Make sure your school board allows fund-raising activities. Check your local board policies.