Good evening Lucinda.
I've booked this holiday, but am in my early 60's. When I went to Japan with JY last year, two of the women were aged 24 & they joined in. On these types of tour age is not important, it's the person!
I've met sprightly people in their 80's on my various tours.
I hope that you make the best choice for yourself.
Regards,
Richard.