HAM radio problem

Hello there,
We are sending this e-mail out because we are in desperate need of
assistance in finding an answer to a complicated HAM radio dilemma. We
are a small non-profit which will be helping to produce a video on the
indigenous tribes of the Peruvian Amazon. A group of about __ of us
will be traveling to the Amazon, east of Cuzco, along the Madre de
Dios river. We will begin our journey in Cuzco (the nearest
metropolitan area), which lies at about 10,000 feet on the West side
of the Andes. From there, we will be traveling about 200 miles east
into a forested region (Amazon) along the Madre de Dios river. Our
elevation will drop to about 1200 feet. At this point our group will
be splitting in three directions (each going on a different tour). We
want to have radios (which we will leave behind with the tribes) to
communicate with each other and with Cuzco. They have a new
eco-tourist program. So we're basically looking to create a radio
system or network keeping three goals in mind (listed below). We are
planning on buying a handheld or portable radio for each group member
(we can spend about $200 +/- a piece for them) as well as any other
equipment we might need. We could possibly buy a new HF receiver with
6 meters or 2 meters added. The local villages and Cuzco have standard
HF receivers.

Goal 1: We would like for each of the members of the group to be able
to communicate with each other via radio in case of an emergency. We
will be in a 25-mile radius of each other.

Goal 2: We would like to be able to communicate with a base camp at a
village that would be no further than 50 miles away from each of the
travelers at any given time. The base camp village has a high
frequency radio. Ideally we'd like each of our group to be able to
reach the camp via radio, but if only one can, that would be ok as
long as each member of our group could communicate with the other (we
figure if one person had the ability to communicate with the village
they could act as a link in a communication chain).

Goal 3: We would like to be able to communicate from the rainforest to
Cuzco. This is two hundred miles away and a 9,000 foot elevation gap.
In Cuzco, there is a HF radio, we are not sure which bands/frequencies
it's operating on. We would communicate only in the case of an
emergency, but, possibly on a regular basis (if the system is
reliable). Ideally, each of our group members would be able to reach
Cuzco, but, again, we're willing to settle for one base radio in the
rainforest, which would be able to reach Cuzco.


What are the general attributes/benefits of 10m/6m/2m frequencies?