Trying to build a nested RESTful route in code?

I've never received a reply on this forum and don't know if I'm doing
this right, but here goes???
Everyone on this forum seems to be doing well with RESTful routes and
I am enjoying them tremendously. I am attempting to use this approach
in a very non-standard way. So here goes the foundation of my
question.
In a nested RESTful route we call it something like this;
parent_child_path(parent)
This is easy and it assumes that we are looking at ONE parent record
to scope the children.

Now, what happens if there are a group of parents built into the
instance variable of the controller?;
@parentscope = Parent.find([1, 2, 3])
We call the nested RESTful route like this;
parent_child_path(@parentscope)

Where I'm stumped is that I'm faced with the challlenge of building
this multi-scoped nested RESTful route in code and delivering it to a
'link_to' statement.
I know you must be thinking, "how did she paint herself into such a
corner". Currently, (thanks to Alex) I'm able to deliver this value as
a field in a 'link_to' like this;
<%= link_to 'Place to go', eval(table.row.routepath) %>

My guess is that I must build a method in the parent model.rb to
assemble this value, but I can find no examples of how this might be
done.
I'm a little desperate here, and will pay money or work for slave
wages in exchange for help.
Thank you,
Kathy
KathysKode@gmail.com