Good question. Although I have not used the Hobie tandems as yet, I have used SIK tandems. They seem to ride pretty well either way, although as expected, the bow will ride a bit higher solo if you are in the aft seat.
I guess you know that there are now two tandem Mirage drive models. The new Outfitter will not be available until some time in October. Since not a lot of dealers stock tandem models anyway, you may want to get your order in now for the older model if you have time constraints. Or you may want to try renting a tandem somewhere to see: (1) if you even like a tandem, and (2) how they perform with 1, 2, or the whole family in them. A good idea would be to find a place where they rent Mirage drive models to see how they perform. You may even get lucky and find a place that rents a Hobie Mirage tandem! My local Hobie dealership, Wilderness Way, also has an active rental service and rents the Hobie Mirage drive models, for example.
Also, to my knowledge, you can't get a tandem (or any other Hobie Mirage drive model) without the Mirage drive. One good reason for this is that Hobie makes similar size kayaks without Mirage drives anyway, so if you don't think you will need the Mirage drive, then why pay extra?
However, I can tell you from my experience, and that of many others, once you try pedaling with the Mirage drive, chances are you won't want to go back to strictly paddling. And don't forget that you can also sail some of the Mirage drive models, and sailing a Hobie kayak is one heck of a blast! Just my$.02.