Athens info

There will be taxis at the port.
You can take the Metro subway but as I recall its probably a bit too far from the cruise ship area to the metro line.

You can purchase tickets for the Acropolis in advance.
This web site has more information.
https://archaeology-travel.com/travel-tips/buying-tickets-for-the-acropolis-and-other-ancient-sites-in-athens/

Do we need to buy tickets to the Acropolis ahead of time?

Probably depends on what time of year your visit is.

From May to October, the X80 express bus runs from the cruise port to Athens city center. The bus stop is located right outside the main cruise terminal A, about 100 meters from the gates.

https://www.oasa.gr/en/visit-athens/x80-piraeus-acropolis-syntagma-express-bus-line/

Outside of this period, the 040 bus operates 24 hours a day and will take you to Syntagma Square in the city center.
You can find the bus stop locations on this map, I have marked the bus stops and the 040 line (only the sections within Piraeus) in green. The X80 stop is marked in orange.

https://www.google.com/maps/d/edit?mid=1b5T69no_NoFqRP30wWaIi3I8WjtjGYI&usp=sharing

The metro is not an option unless you are willing to walk at least 30 minutes to reach the station.

If you do not want to, or cannot, take the bus... Take a taxi.

The site stanbr linked above is one to completely avoid. While some of the advice is fine, every single ticket link on there is a total trap. They're only there for the site owner to rake in affiliate commissions by redirecting you to third-party resellers, this is in fact stated at the very bottom of the main page. Those sites will turn around and mark up tickets by 15% to 30% with zero added value, or try to sell you useless passes that do nothing for you.

It barely even mention the official site, and the link they do provide has been dead for months. The only place you should be buying tickets is directly through the official sources, Hellenic Heritage

https://tickets.hh.gr/en

The Acropolis Museum is managed by a semi-private organization with its own official website and ticketing system:

https://www.theacropolismuseum.gr/en/

I’d arrange for a ride from someone like Welcome Pickups so you know the cost and you won’t get a crooked taxi driver as I did !