I've created a several Access applications, plus several LAMP-based Internet applications. I've interfaced a lot with non-technical people. They don't GET databases. They don't understand normalization or foreign keys or indexes. They don't understand SQL or joins. It's not their area of expertise. They do the actual work of the charity or the company so I'm not in the least bashing them - but they just don't understand databases.
My experience is that after brief training, they'll get spreadsheets. They understand tables very quickly and easily. Explain to them the concept of worksheets. And there's no complexity in opening an Excel file. You just double-click and you are immediately there, looking at the data. Heck, with some thoughtful use of the individual worksheets in an Excel file, you can even get a hint of normalization. Like putting different geographical regions in different worksheets in a single workbook. Having multiple Excel files (workbooks) for different larger groups. People kind of naturally understand that tree-like data structure.
Many people think Access is a toy. But it's still a database and it uses database concepts and SQL. And that is beyond the ken of non-technical types. Spreadsheets are simply much more understandable to them. And ultimately - much more maintainable. And maintainability and understandability is the key here. The charity is going to be here, on the ground, doing their work, long after you've moved back to the States.
There is a fraction of the learning curve with spreadsheets than there is with any relational database, regardless of whether it's a file-based system or a client-server system.
FYI, here are the Excel load limits.