I recently did some voluntary mediation work. I conducted a mediation session for a group of 9 parties, all volunteers, who had fallen into a messy conflict. This was a fab challenge for me and my mediation skills, as it became apparent that as an organisation they'd not dealt with (and hadn't the process to) some historical conflict and poor behaviours.
They were able to agree some future focused action points on communication, constitutional awareness and reviewing their organisational values; and I also advised on having processes in place to hold each other accountable going forward.
It reminded me that volunteers, while not employees, need to be engaged, motivated, respected, cared for, and also managed; and that they tend to have crossover and differences of expectations and needs with employees. This means targeting specific activities to attraction and retention of your voluntary workforce.
There are many other considerations as an employer with volunteers. For example: ensuring volunteers don't become entitled to minimum wage and other employment rights; having a clear line between what are voluntary activities and what are paid activities that only employees do; and ensuring volunteers are trained to do the tasks asked of them.