hello Sam
There are many threads in here regarding the AGE question, I would say if you have a tour and date in mind then ring the office and see if they can give you age range, group size, m/f ratio, or post the question on the editors board and Tim/Julia will get back to you.
I started using JY in 2006 I am now 55 and have my 11th tour booked for next year. I personally do not worry who is what age, I go for the holiday and to meet people, some people are old in age and young at heart others are young in age old at heart. To me it really is just a number. Core age 55-70 with younger and older either side..
All I can say is with out a company like this I would of not been to New Zealand, Kenya, USA many times, Poland, Austria and Tuscany great tours, fantastic experiences and I have met some fantastic people who were strangers and are now good friends. I have not been on the tour you are interested.
All I can say is give it a go, if you have any other questions please just ask.
Cindy