To get around Santorini, we recommend renting a car or a scooter. Cars can be rented for around €30-50/day and scooters for around €15-25/day. Taxis are also available but can be more expensive. One thing to consider is that Santorini can be quite hilly and some roads can be narrow and winding, so it's important to be a confident and experienced driver.
If you have more time, consider adding a visit to the White Beach or taking a Volcano Boat Tour. If you have less time, consider skipping one of the beaches or cutting some time from the archaeological site.