I've got a custom object "Invoices" tied to my Opportunities, so Opps have 1 or more invoices. Each invoice has a "date to be sent" field.

What I'd like to do is auto-generate an email every Monday morning that notifies each User of their Opportunities and with Invoices scheduled to go out < Next 7 Days. The purpose is for them to go in and edit the Invoice to either flag is as "Ok to send" or to move the date back to a more appropriate time.

I'm trying to accomplish this using a VisualForce email template, but can't for the life of my figure out if the relatedTo should = User or Opportunity since I want it to list all of the relevant invoices for Opportunities owned by the User.

Anyone have any guidance on how best to implement something like this?