Wow what a cool prize to win. This will be an awesome experience.
As a fan of good food I can recommend to avoid the big restaurants close to famous places. Try small local bars/bistros who serve tartiflette, canard,cheese plates. Last year I was in Paris and as a food lover I did my research. Here are 3 restaurants I really liked because of the combination of quality, price and atmosphere.

https://www.tripadvisor.be/Restaurant_Review-g187147-d3192219-Reviews-La_Petite_Rose_des_Sables-Paris_Ile_de_France.html
Amazing experience, great owners and only 8-10 places so great atmosphere. Food is good but not the best but it's the total package and the kindness that makes the difference here. Best to make a reservation.

https://www.tripadvisor.be/Restaurant_Review-g187147-d10201111-Reviews-Pedzouille-Paris_Ile_de_France.html
A cosy place with a cool interior. Each day 2 different main dishes but good quality and typical French. If you like cheese, you really have to take some flamed camembert.

https://www.tripadvisor.be/Restaurant_Review-g187147-d4228364-Reviews-Les_Climats-Paris_Ile_de_France.html
Top top quality, they have a star and it's well deserved. Of course this is not cheap :-p. Not everyone wants to pay this for food.

Never been in Athens but visited some Greek Island. Here are some foods you need to try. Dolmadakia, Mousaka, Gyros, Keftethes and different kind of sweets.

Enjoy your trip and have a safe flight. I'm looking forward to your posts!