Is it ok to delete the Amazon .apk files? I have backed up all of my .apk files to my laptop. Can I delete the .apks in the Amazon venezia cache folder without detriment and be able to put them back on the sd card and reinstall from there at a later date, if I want to?
You can redownload them any time you want or just install them using a file manager, no need to put them back there.  

If you backup them to your PC it's a good idea to use something like this to keep track of the various apks.