Keeping in mine your final "at your own risk" which option is the least likely to cause an issue?
That's a hard question to answer. I would estimate that an iframe is the least likely to break other parts of your site but the most likely to not work well in mobile. The "widget" option is likely to be the most functional, especially on mobile devices, if it works at all.
I would try both on an unpublished site, if possible.