Green level JR Rail Pass

I have purchased a JR Green 14 day rail pass (61,200) for mid Sept. I will need to travel with a cane and one piece of small luggage. I will be travelling from Shibuya-Tokyo-Yufuin with some local usage in Yufuin and Shibuya-Shinjuku. The Hikari pass noted after I purchased the pass that "most" Hikari trains do not have green seating. Is the JR Green level worth the cost if it can be used for the Tokyo-Yufuin trip? What does "most" Hikari trains mean? Should I try to exhange the green to an ordinary pass with a 15% exchange fee cost? Should I cancel the JR Pass and pay local fare at the time I travel ie Nozomi?
Thank you very much

Raven,

West of Okayama, there are no Green cars on Hikari (Hikari Rail Star) services. These services do however have superior standard class seating (2+2 as opposed to 2+3) if you reserve seats in advance. The train from Hakata to Yufuin also does not have Green car seating, although I think that train is pretty comfortable too.

Raven, do you have a plan to stop by cities between Tokyo and Yufuin? (ex. Kyoto, Osaka) If not, it is more reasonable and comfortable to fly from Tokyo (Haneda domestic airport) to Oita airport (about 1hr from Yufuin). I did a quick search and there're still discount tickets available for mid-September. (less than 20,000 yen for one-way)

With JR pass, you cannot ride Nozomi fastest shinkansen and you're most likely to change shinkansen at Shin-Osaka station.