Best way to create child work items (a very repetitive task)

I have a situation where a parent work item is defined much earlier in our team’s process.  Then at a point, there is a need to create many child work items for that parent.  Each of the child work items will be of the same work item type (but different than the parent type) and two unique (enumerated field) values must be entered for each child item.  The number of child items can also vary from one to many.

What is the most efficient way to do this?  I found the menu item “Link to New Work Item” which is certainly what I am trying to accomplish.  But this requires selection of the Link Type (which will always be “Children” in this case) and selection of Work Item type (which will always be the same for each child).

The way our team usually works, it seems to make the most sense to start with the parent and create the children from there.

Would a work item template accomplish this?  I thought it might.  But how would we handle the linking using a template given that the parent is already created at the point we want to create the children (we don’t want to create another parent only the children)?  And how could we use a template and specify how many children we wanted to be created at one time?  Can the number of items created by a template be set to vary?