Re: What to use to manage club(s) database and classes
LibreOffice is a good open source spreadsheet/word processor/presentations and other office package. It's updated regularly and runs on Linux, Windows, and Mac systems. I'm not sure about their database program.
MS Excel and Access link and can refer to each other as long as the data files are on the same network and you can probably link it all up with Word documents for communication with members.
You'd spend a bunch of time setting it up to do everything you want it to do. Can't comment on the security - not my strong suit.