Your husband can deduct for some out-of-the-pocket expenses when volunteering.   Forming an LLC is likely  not necessary.   These deductions are personal deductions claimed on Schedule A of Form 1040

• The value of his time is never deductible as a charitable contribution.
• Travel, meals, and lodging expenses are deductible if your husband was away from home overnight while performing services for the organization.
• As far as automobile expenses typically mileage is deducted.   Here is a link with further details and current mileage rates:  Standard Mileage Rates
  
  Here is link with additional information on deductions for donated work:  Deductions for donated work