One thing I will add to my recommendation of VSDC is that you shouldn't be put off by its many features. I just create a project, add 50 to 300 photos, set them to display for 3.5 seconds each, add a random transition between each, and add music. The music can be one or several 'out of copyright' tracks. The music should be slightly longer than the slideshow. Then trim the end to be a fraction longer than the slideshow, and finally fade the music out over the last few seconds. Save the project, export it to your chosen format and upload it (over night, it takes a while to upload).
Apart from the export bit (which runs in the background while you do something else), the whole process takes less than five minutes per film. My family history films are set as private as they contain living people.
Martin