It is the full day Athens and Cape Sounion tour, but we are modifying the itinerary. On Mondays, the New Acropolis Museum is closed and they do the Panathenaic Stadium, Tomb of the Unknown Solider, the Temple of Zeus, the Old Palace and Changing of the Guard instead of the museum. We are visiting on a Wednesday, but they said it was no problem to do that itinerary on our date.
The full day tour for four people is 240 euros. We are adding a guide for the Acropolis portion for 90 euros (2 hours). If we wanted a guide for the Acropolis and the Museum, it would be 150 euros for the guide (for about four hours).
Larger groups have to use a minibus - the sedans only seat four plus the driver. The minibus seats 12 (I think) and is 550 euros for the full day tour with an all day guide. The full day tour with a half day guide is 420 euros. That would be cheaper per person if you have a large group, but we like the flexibility of a private tour for the four of us. If the kids are getting antsy, we can change it up.
I'm not sure what the full day tour in a minibus without a guide would cost. The half day Athens tour in a sedan was 150 euros and the full was 220 euros (Athens only, not Cape Sounion).
Here is the link - it is tour 2 on this page:
https://www.athensbytaxi.com/privatetaxitoursfullday.html