Hi smudger1,
There are 7 people booked on the Peru tour alone, and 5 people, with 1 person optioned, booked on the Amazon add-on. This takes the Peru leg of the tour up to 13 people - 4 of which are male and 9 are female.
So as usual, you check your luggage in at Birmingham, and you bags will be checked all the way through to Lima - meaning that you do not have to worry about you bags on your journey. In the unlikely event that you miss your connecting flight due to an airline delay, the airline will put you onto the next available flight. On arriving in Amsterdam, you will go from one gate to another where there will be seating or there will be a transit lounge where you can wait until you depart on the connecting flight.
I hope this helps, and if you have any other questions please do not hesitate to ask.
Kindest regards,
Monty