Good morning Cazley, 
At the moment there are 9 travellers booked in total, three of you are booked for the main Discover Vietnam tour only with the other 6 staying on for the Angkor Wat add-on. 
The age range of the group is from early-50s through to early-70s - it's still quicte a way off so if you ask me again in a month or two I will happily give you an update on these numbers. 
Kindest regards, 
Julia