The advantage to making an FXL is that your family could view the document and play with any interactivity in a mobile device as well as iBooks or Adobe Digital Editions. FXLs support many interactive features that PDFs don’t, including animations. And though PDFs support buttons and MSOs and videos and such on the desktop, they usually fail on mobile. FXL ebooks, opened in iBooks on an iPad or iPhone, handle those w/aplomb.
The file that results is an .epub instead of a .pdf. So they just need an eReader that opens EPUBs. Which iBooks does on iOS devices. Android eReaders have a spotty record of what interactive features they support.
In sum: If your family/readership is mainly using Macs and iOS, and you want to include more interactivity, give it a shot. It’s as simple as exporting to EPUB (fixed layout). If most everyone is on Android/Windows, it’s a more difficult row to hoe.
AM