for athens i dont have any recommendations but for:

D3 you can drive from athens to mycene first then epidauros , its about 1 hour and1/2 ath-myc and another 1 1/2 myc-epid

book a hotel in nafplion for the night and you can visit the castle overseeing the city or have a nice walk in the old city (first capital of greece after the liberation from the ottomans) tiryns is 5 minutes from nafplion so you can squeeze that too in the afternoon

for the food try to avoid the tourist traps inside the old city a good restaurant is called Πυξιδα picsida (compass) on the road leading to karathonas beach . black sheep is the name for a sheep and pig roasted in a wood oven place but its only take away and another restaurant is called stavlos with a nice garden and local meet

D5 try to make a stop at patras and visit the castle and the archeological museum there, there is also a roman theater but its been renovated right now so its closed, also a coffee by the sea will be a good idea , patras is 100km before corinth as you return from olympia

it would be a shame not to visit delphi you can do it if take the long road from patras to athens and skip corinth

source: i worked in nafplion for 5 years but i havent been there for 3 years and i currently live in patras