Ah man I would have loved to see the breakfast portion as well! How was the food overall? I saw some mixed reviews about it. We’re going there this September! Excited to go but nervous about what they said about the food :( did you guys do anything else in the hotel?
Overall, we liked the food, especially the sashimi and beef shabu. You can see the breakfast portion in this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-KImNbpK_BDw.html :) We didn't really do anything else in the hotel, just relaxed in our room and enjoyed the onsen. That's exciting, hope you like it! :)
Hakone Airu is approximately 8.9km from the Open-Air Museum. According to Google Maps, it would be about a 20 minute drive, or 30-50 minutes using public transportation. We're not sure since we didn't have any vegetarians in our group, but you could try to make a special meal request to the ryokan.
It was our first time trying kaiseki so we didn't have anything to compare it to, but we enjoyed the food. It was also beautifully presented and there were a variety of dishes to try.
Breakfast and dinner was not served in our room, but in one of the private dining rooms on the same floor as our room. The private dining rooms were located outside our room through a hallway, and we used the same private dining room for breakfast and dinner for the duration of our stay. :)