I think you had better resign yourself to the fact of paying them. While either of the suggestions you make certainly would benefit them, you'd be hard pressed to convince the DOL that either was benefitting them more than you unless you were prepared to PROVE (and your proof had better be iron-clad) that the duties they were performing were such that if the interns were not there, you would NOT have to have paid employees perform those duties.
Unpaid interns are pretty much a thing of the past. I eventually ended up in a program where, while we did not pay the interns directly, we paid a stipend to the schools and the schools paid the interns. The DOL does not like people working for free and the requirements for you to be allowed to do so are VERY stringent.
You need not pay more than minimum wage; you need not provide them with benefits. But they do count as employees, albeit temporary ones, and they need to be paid.