You are going to all the best places! Check out my signature for Paris and Iceland trip reports.
We are headed to Iceland this summer again. Iceland is no joke as far as needing to book accommodations well in advance- you cannot wait to book hotels or airbnbs. I would just do it in the next couple of months and make sure you book refundable options. Iceland will be a nice treat after being in European cities during the summer heat. Just be sure to get out of Reykjavic and stay either in the south coast or in the Golden Circle.
Flights
Agree with the AF/KLM options. They offer a new stopover benefit in CDG for free, so that means you can continue onto Athens for no cost. It needs to be booked over the phone. Refer to the wiki on
FT for an easyish guide. Iceland Air also offers a free stopover benefit, but this would be a cash flight. Check to see how much the mark up is on a one-way cash flight vs the round trip to be sure you aren't really overpaying.
Paris
Not sure of the highlights you'd like to hit in Paris, but the Eiffel Tower is not really the most central location. I personally would recommend staying near the Louvre, as you're walking distance to the Louvre and Royal Gardens, Notre Dame and the Seine. Transport to the Eiffel Tower when you want to visit there via subway, uber or taxi. If limited time, consider a tuk tuk tour to hit the highlights around Paris.
Oia
You can ferry or fly here from Athens. Ferry experiences in Greece are pretty cool. I think you can also do an overnight ferry from Athens, if that saves travel time and a hotel. We stayed in this
AirBNB cave house right on the caldera in Oia, and the view is literally maybe the most beautiful I've ever seen. It's so beautiful it's almost impossible to truly explain how beautiful it is. Greek breakfasts (included) are the best and I still remember these croissants as being some of the best we've ever had. A couple nights in Oia is probably plenty. You can do the
Red beach, black beach, white beach tour from near Akrotiti. No need to book in advance, just show up at the water taxis. From Oia, another cheap activity: you can walk down a few hundred steps to the small marina and enjoy a meal waterside (pass on riding the donkeys as they are abused). For sure visit the bookstore in Oia.
I recommend buying AirBNB giftcards at a discount, or you could PYB with a CSR if you buy gcs at a grocery store. I like to buy mine at a grocery store that also offers fuel points bonuses. Don't forget to use the British Airways AirBNB portal to earn 3x Avios on your AirBNB bookings.
Message me if you need any help. You are going to plan the best trip!
View attachment 775973
View attachment 775974