Limiting the Ability to add Child Records Based on Drop Down Field Value

Thanks Mark,  couple questions.  My two tables are as follows..."Dealers" (Parent Table) has  many "Picks" (Child Table).  Which table will contain the [# of Allowed Children] field?

In the relationship where does the Summary field go?  The "Dealers" table or the "Picks" table?

When creating the Summary field how is the following setup?