If you need to value some kind of voluntary work of the members of the community, a good starting point is the average net hourly wages within the society.  ILO has also published a manual on the valuation of voluntary work.

http://www.ifrc.org/docs/IDRL/Volunteers/ILO%20Manual%20on%20Measurement%20of%20the%20Volunteer%20Work.pdf

The first step is to examine the purpose of exercise which may: 

• Cost determination
• Cost minimization or cost control
• Cost consequencesCost effectiveness
• Cost-utility
• Cost benefit

In estimating costs one needs to consider:

• Opportunity cost = economic costs
• Cost is foregone benefit of a recourse in it’s best alternative use
• Market price may not reflect correct cost
• Need to estimate shadow prices/social value of resources
• No market prices: donated goods, volunteer time
• Distorted price: market price of labour
• Unstable prices: exchange rates
• Capital goods which have life – yield over a period of time

The third step is to define the perspective 

• Society
• Government
• Patient
• Payor
• Provider
• Research

While costing, besides direct and indirect costs, pay attention to

• Productivity costs 
• Production loss, replacements costs

Approaches

• Human capital approach
• Travel, waiting and loss of wages
• Friction cost approach – societal perspective
• Transaction costs associated with the replacement of a worker
• Substitute labour is less productive – training cost
• In case of acute illnesses – long-term
• For short-term absences, the friction cost is zero

I hope this helps.

Best

Regular cost-benefit analisys can be used, but concerning family labor do not value it at market price unless the member of the family left a job to work at the farm or community. The cost of that labor is the diference betwen monetary income and monetary expenses