HI Robbie
We are going through a similar process with our alumni. I’m chair of the St Peter’s School, Cambridge, NZ Alumni. We have three main areas driving requirements.
1. As an incorporated society we are a separate legal entity so have certain legal obligations. eg maintaining member records and carrying out charitable activity.
2. We are currently developing a 10-year plan that will lead to the schools 100th anniversary so have a set of objectives we wish to achieve by then. These also drive activities in the short term.
3. We have a very professionally run advancement office with a new director so this means we will be able to step down from some activity we used to do. We are therefore working on an MOU with to ensure we are aligned and can support each other as best as we can so this will also drive some requirements.

I too was interested to find out how others do it so have approached a number of other school chairs/vicechairs to arrange a get together to discuss.
Happy to do a call to chat more.
best
David Wybourne