Possible to create Child records on a closed Opportunity?

Hello,

Our Opportunity records allow users to create many child Opporunities within one parent Opportunity.  However, a lot of our Parent Opportunities have been closed and we still want to be able to create child records directly from the parent.  There is a grid on the parent Opportunity form that allows users to create new child Opportunities.  Is there a way to let users create these child Opportunities from closed parent Opportunities without reopening them?

Thanks!