Car & Tour Greece/Athens Qs w/ Elderly Family

There are two decent hotels near the airport. First is Peris. Its about a 15 minute shuttle ride from the airport. Shuttle is free. Its just on the side of a village so appears to be remote. Its well priced, breakfast is included and its a good place to get bedded down after a long flight.
Second is Avra hotel in Rafina. Its a better hotel, just a bit longer commute and free shuttle service. It is in Rafina so it is in the town close to the center and the ferry port. I do not have your dates but there does appear to be a daily ferry Rafina to Paros.

Or you can return to the airport to fly. We almost always fly to our first island but if you are in a port with a direct ferry its convenient, you don't have to get up early the next morning so that might be a good option.

I would respectfully suggest you have a flaw in your plan.
After Paros you might want to consider doing the VRBO and end in Athens. Its good to be close to the airport before your return flight.
I would suggest you rent the vehicle at the airport. That way you do not have to drive in Athns traffic. You will be on a major 6 lane highway from the airport.
We always rent from ACR Athens car Rental. I do not know if they have vans though. Look them up they have a good reputation.
The bus system can be a bit tricky in the Peloponnese. A vehicle rental will be a good choice.

Since your flight arrives too late to take a flight to Paros on the same day, just like stan here is what i think is the best solution for you but it's only possible if you arrive between the beginning of June and the middle of September (due to ferry schedules)

If so, this will allow, as you hope, "convenience and limited logistical, and a nice trip for your parents and aunt".
Any other opinion that would suggest taking a flight from Athens to Paros the next day is in my opinion a huge mistake.

The solution is to take a ferry the next day to Paros, not from the port of Piraeus but from the port of Rafina.

Here is the plan:

You book the rooms at the Avra ​​hotel in Rafina for the night of your arrival in Athens.

https://www.hotelavra.gr/

This hotel has a free Airport-Hotel shuttle that will take you to the hotel in 20 minutes. (You mention that you will use the shuttle when you book the rooms)

At the airport, when you have picked up your luggage, you go to exit 5, the shuttle is located 30 meters further in the shuttle parking lot.

You can have your dinner in Rafina. The hotel is located near a number of restaurants / taverns either in the center of this small town, evening at the port (it also has a restaurant).
The hotel is very good for spending a night, the rooms are not huge but comfortable and have a balcony with seaview. Staff are efficient and friendly

The next morning (between 7am and 8am) you take a ferry to Paros. The port is a 5 minute walk from the hotel.

You will be in Paros before noon.

We did this way last year. At 11:30am we arrived in Paros, time to pick up the rental car, go to our accommodation, put down our luggage, at noon we ate in our favorite restaurant in Paros.

Moreover the trip by ferry is the best and the most pleasant way to arrive in a Greek island.

My mother and aunt can walk, but have difficulty with uneven terrain
and are slow.

Again, it can depends on the time of year you will be in Athens.

Due to the extreme heat of summer, this visit can turn into an ordeal for someone who has difficulty walking.

The southern access is less sloping and there is more shade as well as benches to take a break.
There is also a lift for disabled people but I don't know the rules for using it.

You can download this map indicating all the accesses, including the elevator for disabled people:

https://drive.google.com/file/d/1IqI-bfYbaZ0Wf_cS1B5InLFG5YRxcBST/view?usp=sharing

Thanks for the replies so far - lots of great info and tips. I edited my post to add that we will be traveling in late July/early June (of this year).

Great advice so far: free shuttle to Avra Hotel upon arrival in Athens, then next day ferry from port of Rafina to Paros.

If you can change dates on the VRBO, then fly from Paros back to Athens and pick up rental van. Five days later, return van to airport, taxi into Athens for 3 nights, then taxi back to airport to fly home.

This plan all hinges on the possibility of finding a van large enough to hold seven people (if I counted correctly) —- AND their luggage. So you will want to impress upon everyone the need to pack lightly, in just a carry-on size suitcase.

Finally, hotels and planes are booking up quickly for this summer so you’ll want to finalize your itinerary as quickly as possible.

If you can find a 7-person van, I'd take that over a long bus ride to the Peloponnese, especially since you are traveling with elderly relatives. In my opinion you'll also need the van to visit ancient sites while you're staying in Kalo Nero. Greek drivers are aggressive, so have your husband read some information about driving in Greece in advance. For example, drivers tailgate to make you drive on the shoulder so that they can pass you. Also, if possible, pick up the van on the outskirts of Athens so that you don't have to drive in the city.

As for your mother and aunt, every ancient site I've been to has cobblestones or walking other challenges. One solution would be to ask for wheelchairs. Another might be taking hiking poles--be sure to include rubber tips which are required at the Acropolis. I would definitely look at travel sites for disabled travelers to see what the problems might arise for them. Start with Rick's page at https://www.ricksteves.com/travel-tips/trip-planning/travelers-with-disabilities.

Be prepared and enjoy the trip of a lifetime.

About ferries to Paros, check with Golden Star Ferries.
The Superexpress leaves daily at 7.15am.
He arrives in Paros at 11:20 a.m.

https://goldenstarferries.gr/en/

Fastferries' "Fast Ferry Andros" is slower and only departs on Saturdays and Sundays.
Departure 7:30 a.m., arrival 1:50 p.m.

https://fastferries.com.gr/en/

To see all the ferry options, see:

https://www.ferryhopper.com/en/

Book a week in advance (no need to book months in advance).
With the web-checkin option you will get E-tickets with a QR code.
You can print the tickets or/and keep them on your smartphones.

You can board the ferry approximately 1 hour before departure time.

Why did you chose Kalo Nero as a base over the Nafplio, Tolo region (Mycenae, Epidaurus, etc.)? Was it because you are traveling during the busy tourist season? I’m looking at a similar itinerary and noticed there’s a motorway to Kalo Nero. We also have one in our party with mobility issues and prefer to have one or two bases and to keep our driving to 3 hours max a day.

Noelle, very often an odd location means people fall in love with photos on the internet and what looks like a bargain price, before they seriously study a map, or understand the realities of driving in Greece -- e.g. MUCH slower than USA, and on secondary roads, somtimes only 30 mph. Let us hope that OP has not "locked in" to a Messine-area place because of apt fotos. IN Greece, 90% of decision should be based on location, location, location.

Thanks to all for your continued helpful advice, really appreciate it. We've booked Adva Hotel with ferry tickets from Rafina to Paros. It's too late to change our Peloponnese VRBO (should have posted here earlier!) but looking forward to the challenge of coordinating logistics on a rental car with Athens in the middle of the trip. :-) Thos, thank you for the link to the Rick Stevens page for travelers with disabilities - it lists a tour guide in Greece who is knowledgeable about accommodations on tours, so I will check with them about options for an Acropolis tour (that's the one I'm mostly worried about with my mother and aunt). Noelle, I looked at many different rental properties near the coast on the Peloponnese and picked one that suited our somewhat difficult checklist, after reading many reviews of the property, as well as researching the area. It seemed that Kalo Nero was close-ish driving to a few archeological sites of interest to me, walkable to a village, a little off the beaten path, near a beach (albeit perhaps not a great swimming one, but I figure we'll get our swimming fix in Paros) and with several hiking trails nearby for my father. We won't be able to see the entire Peloponnese in 5 days from that base with 2 kids and 3 elderly adults, and I don't have any illusions as to that. Janet, I of course hope that my hours of internet research will prove to have yielded a good spot where my family can enjoy a once-in-a-lifetime trip, but of course, you never know until you get there! That's part of the fun of travel to a foreign county, right?

I looked at VRBOs in Kalo Nero and saw some beautifying homes at really affordable prices. It looks like a great area, with a variety of activities and historical sights, and it’s accessible from a motorway instead of those narrow winding roads. It looks like a great choice.