I'm not a professional, but have done a good number of photo books. I believe your mother would most enjoy the book if you divided it into sections. First, sections of places, then of people, miscellaneous landscapes, etc. I would not have a table of contents, but would introduce the sections with text, maybe even separating the sections with a page that has the introductory text. Captions are nice, and add interest to the book. This doesn't have to be overdone - maybe just a sentence or two.
Very nice of you to do this - I'm sure your mother will treasure it!