I only have an eink Kindle, a couple of generations old. It has 3 fonts: 1 serif, 1 san serif, 1 monospace. Remember that a font will take up something like 500KB and the Kindles have limited space.
The Kindles with front lights, and the Fire tablets, have more space, and run the K8 format rather than the older K7 format, so they might include more fonts. I don’t know.
Since you use Georgia and Arial, the simplest way to go would be to specify a san serif font for the Arial and leave the rest serif (depending on which you use more often in the text). That can be done with a span element surrounding the san serif text. It will look different from the main but not exactly Georgia and Arial.
But that span element might also be trouble for you: you would I think need to compile to epub and edit the book in Sigil or Calibre, or you might be able to compile to mobi and then edit in Calibre.
Also if what you want is to have different ‘voices’ for different passages, or titles, you might consider monospace, which you MIGHT be able to do right in Scrivener and get it to translate to the mobi compiled output; I am not sure about that.
Kindle, the new ones, also have a semi-pdf style format, but I don’t think that Scrivener has the capability of outputting that; it might be some special sauce that you must deal with Amazon directly to get.
Remember also that with ereaders and ebooks in general, the philosophy is that the publisher supplies content, the maker governs the overall look, and the reader chooses specific looks. The reader gets to choose san serif or serif, as well as font sizes, kerning, leading, on my Kindle device - no matter what the publisher or author wanted. Ebooks are not, generally, for those publishers who want to control the reading experience.
The only Kindle book I ever got that had an embedded font had a page after the title page saying something like, “This book has embedded fonts and will look better if you use those fonts. Do you want to use those fonts?” The default, do-nothing-on-my-part as reader, showed the book with the default font. I had to enable the book to display the embedded fonts. If you got the Georgia and Arial embedded, and I bought your book, I could still ignore the look you want.