On our July 06 Essential Europe trip, the ages varied from 9 to 80. It was a homogeneous mixture of ages

There was a couple celebrating their 25th anniversary, while there was this lady with her two daughters out to celebrate her 80th birthday.
Every one was so friendly, and age did not matter. We are in our late thirties and we found enjoying gondola rides, restaurants etc with couples in their later fifties and early sixties. I think everything depends on you and what you decide to make of the trip.
Good luck and bon voyage.