Creating child records

Hi,
 I am working on a custom entity with two forms and based on the security roles, we are letting users access those forms.
 Now, I am trying to copy a form1 data to form2 along with its child records(all). I was able to create a workflow for copying form1 data to form2 but not able to copy the child records(form1).
 I've looked around for options and seems like plugin can do this job efficiently. How do I trigger a plugin when workflow creates form2(copy of form1)? There is a field which gets updated in the form1 through this workflow. Will an
update step work? If so, how do I get the newly created form2 and associate child records to it?
Please give me some suggestions on this.. I might be overdoing things which could be easier. I am still learning and would like to learn from your experiences. Thanks for any help.