Custom Sharepoint sites for entities

Here is my scenario.  I have the following custom entities. 

Custom Entity1 - For each record create a top level sharepoint site. 

Custom Entity2 - For each record create a site collection under Entity1 sharepoint site.

Custom Entity3 - For each record create a site collection under Entity2 site collection.

I have custom sharepoint services, that create all of the sites and site collection. 

I've created workflows, on Entity1 - create ( call custom sharepoint services to create site). 

In each case, sharepoint services returns the site address. 

Should i use the SharePointSite entity and call the service.Create(SharePointSite) for creating an active sharepoint site and site collections in teh CRM system?

How do i tie each site to the correct entity1 records? Meaning, if i add documents to entity3, they should go to site collection for entity3.