You definitely need one pair of P300s for Central Post to/from the Mountain Peak.
How many more P300s will depend on line of sight visibility from the Camera Sites to
the Mountain Peak. You will need one P300 Root Bridge facing the Cameras, but also
one P300 NRB to connect each of the Cameras to that Mountain Peak RB.
You can support 10 x NRB to your Mountain Peak RB, if all 10 Cameras are within
a 30 degree horizontal and vertical radius. The Distance configured on the bridges is
very important. You would set the Mountain RB Distance to the median between the
closest and farthest Camera NRB, and close to the actual Distance for the RBs.
If your Camera Sites are not all within 30 degrees, you might need two RBs on the
Mountain, and direct half of the Camera NRBs to each one on different channels.
If your Cameras were closer than 200m, I'd suggest trying the T300 series of outdoor
AP, that might be able to Mesh from the Mountain Peak to some of the closer Camera
Sites. This of course would require a ZD to have mesh function on the T300 APs.