Hi Brian and welcome to the forum. Several good points have been made here, and here's some more input.
Tandem vs. single: This depends on your personalities. If you tend to be competitive or prefer some personal space occasionally, singles can be nice. With a tandem, no one gets left behind, you can each have your own activity or pace and still enjoy being together. We have a tandem and really enjoy it. I go for the exercise and she listens to her books in tape, pedals and relaxes. With two Drive systems running one boat, it's easy to cruise along at an easy clip and see lots of scenery. The front seat in tandems can catch a little spray in chop and head winds. In cooler weather, you might want to look into a dodger for the front. If you're on the road, one boat is a lot easier to transport than two even though the tandem is a little heavier to load. As you know, tandems can be used solo also.
Equipment: Your list looks great. I don't think you need a safety flag, especially if you have bright colors, but it certainly doesn't hurt. I've never tried the dodger, but keep it in mind if there is a spray or chill problem. On pfd's personal preference comes into play -- read some reviews and try some on. Shop around -- there is something for everyone!
Oasis vs. Outfitter: We use the Oasis and are now on our second one (after 6 years using the earlier generation). We have also used the Outfitter. Once aboard and going, you don't notice much difference. The Oasis cruises a little faster, is a little drier in chop and doesn't pound or slap as much in chop and wake. The initial stability on the Outfitter is better, although both are plenty stable. They're both excellent -- pick the one that appeals most to you.
Transport: There is a lot written on this in the forums. When you buy, see if you can return it if you don't like it. What ever system you you end up with, you will learn to optimize it to your situation (using a step ladder, carpet strips, etc).
Here's another good discussion on the Oasis (formerly called "Mirage Tandem") vs. Outfitter:
http://www.hobiecat.com/community/viewt ... dem+single
Be sure and rig a tow line in case you need to tow anyone or tie up. I use parachute cord ("550" cord) -- small but strong. It's also great for securing gear tethering paddles, etc.
