Newer versions of Kindles have better support for fonts but unless you have very good reasons for selecting specific fonts, like a children's book, it might be better to stick with the defaults. There are several things to consider:
Older versions of Kindles may render the book differently - you'd certainly have no control over that.
Readers have preferences for the font style, size, spacing etc and might not appreciate those being overridden,
Kindle Version 8 (KF8) has a number of built in fonts that you can specify in CSS - you can even embed your own fonts but Amazon don't recommend this.
You can find more details in the Kindle Publishing Guide Lines
If the software is free, you have only your time to waste creating an epub. If the results look ok (and the software might disregard font info anyway for an epub conversion), you can use other free software to convert to Kindle format. Calibre will do this as will KindleGen. As RC mentions, I'm pretty sure you can upload an epub file directly to Amazon and it will convert to Kindle and you can view the results in the previewer.
Good luck and prepare for plenty of head scratching.