N2 your self analysis for choosing an area of volunteering is nigh on perfect methinks. I went the 'completely different' route and ever regretted it. Rather found those who continued in their field of knowledge often referred to 'it was better in my day' and were often reluctant to embrace new ideas/technology. Good luck, GoN, with whatever you choose. If it ends up less than ideal you can always change your arena. Seems there's much help needed almost everywhere.
34 year old assisted euthanasia
Static caravan purchase is it worth buying