Hi CDNPolar,
Trying one more time as my posts keep getting deleted... re-posting a refined version of my prior post.
Thank you very much for taking the time to respond to my question. I have been in touch with Hurtigruten on this topic and they informed me that our return will be to EZE, not AEP (the one closer to downtown). They indicated that the AEP arrivals are for passengers with a post-cruise itinerary with Hurtigruten. I am aware of the 10pm recommendation and our flight leaves a little after 10pm.
The ship is scheduled to arrive at Ushuaia around 8am in the morning - which should (hopefully) give us ample time to get back to EZE on the same day (barring any weather related delays).