Yes, you can do this by having your free plus shipping offer as the primary offer. Then set up a secondary offer with the recurring charges. Make sure it is a free trial. Make sure both are memberships. And it must use credit card for checkout. Then go into the primary offer and choose the option for "combined memberships".
You can then checkmark to allow or not allow the option of checking/unchecking the continuity.
Keywords: continuity membership
