Suggest that the button generate a file with a .csv extension and send that with the headers as a download so that users get a file they can open in a spreadsheet program easily.
I prefer it as it is. Usually I copy/paste it into Excel
o In the browser window select all then copy (Ctrl+A, Ctrl+C)
o In the Excel window paste (Ctrl+V)
Being forced to download and open a .csv file seems like more steps to me. If I want to save the .csv file instead of copy/paste it is simple to use the browser's Save As command to write the window to a file.