Well your own research shows that most mail clients don’t do iFrames, so what do you think can be done?
Your best bet is to get a static image of the map and embed it as an image in an HTML email. Put a hyperlink on it to the “full” map on Google Maps.
To do this manually in Gmail:
- Go to http://staticmapmaker.com/google/ or similar
- Enter the location
- Copy the map image to your clipboard and paste it into an email
- Copy the
hrefof the anchor in the section “Map with link to Google Maps”
- Select the whole image (put the cursor to the right of the image, and press shift + left arrow
- Press ctrl+k to hyperlink the image
- Paste the url from step 4 into the Web Address field