[Dridzt]

Function names are case sensitive so for starters you need

local frame = CreateFrame("Frame", "myframename", UIParent)

Secondly you can store your frames in a table for easy iteration but frames are tables themselves.
So you could just as well store the references to the children on the parent frame.

for i=1,5 do
  frame.children = frame.children or {}
  frame.children[i] = CreateFrame("Frame", "child"..i, frame) -- or your custom frame creation function
end

for _,child in ipairs(frame.children) do
  -- manipulate the child frame
end