grammatical number - children as adjective as opposed to child

In computer science we talk about binary trees as connections of nodes which of which have either zero or exactly two children. Furthermore we talk about "the parent node of a child", "the left child node of a parent", and "the right child of a parent". If I want to talk about both left and right, should I say "both child nodes" or "both children nodes"? As a native English speaker, "both children nodes" sounds more natural. Furthermore I'd say "both these nodes", not "both this nodes".

Another example is if I'm talking about member of a club: I'd say "This rule applies to all women members", not "This rule applies to all woman members".

My guess is that if I'm using a noun as an adjective, and the noun has an irregular plural form, that plural form can be used as an adjective. However, if I'm using a word which is an adjective only the singular form of the adjective can be used. "all women members" but "all female member" and never "all females members". Here female is really an adjective, not simply a noun being used as an adjective.

Or does it rather have to do with the fact that the "en" ending marks an irregular genitive form in Old English, and this usage as an adjective is just a vestige that old usage?

Or perhaps is this just an artifact of my particular dialect, and not standard English? Whatever that means...

Which is correct? "both child nodes" or "both children nodes"? Or do they perhaps have different meanings?