I have never heard of a child having seven-first names. Two middle names or two hyphenated first names, yes, but not seven first names. Unless these names are family names, I wouldn't go with seven names. What name would you call the child?
Out of the names you've chosen for your son, I like
Gabriel,
Montgomery, and
Charles, but in a different order. This is how I would do it: Gabriel-Charles (First names)
Montgomery (Middle name).
Out of the names you've chosen for you daughter, I like
Rosa,
Eliza, and
Michelle, but in a different order. This is how I would do it: Eliza-Michelle (First names)
Rosa (Middle name).