If your mom have a standalone able to play avi, the simplest thing to do is to burn all movies and pics as a data disc.
Usually these avi-capable standalones have a menu that ask you what you want to play so it's sufficient to insert a disc and select what you want to see with the remote control.
If you select an image, then the player will start from that image and will show all pics in the disc in a slide-show mode. You can always skip pics with remote control.
The best way is to do a test putting some pics and videos on a disc, with a rewritable for example to not waste media, and see if results are acceptable.