I've used LibreOffice (or OpenOffice as it was known before), and a problem with this approach is that your family will still constantly ask you to install Office and crack it for them. And those who don't know any better will ask your help to open the PowerPoint their friends keep sending them.
Not to mention that LibreOffice doesn't have an easy to integrate backup solution, nor an easy way to share big photo folders, let alone a decent mail client.
LibreOffice is a good thing at what it wants to be. But it's not comparable to what MS is offering in the form of a subscription though. You don't just switch and only replace the word and excel alternative...