Nothing wrong with automatic transmissions in daily drivers. I love mine. It kicks ass.

RodneyWright wrote:
OK, so what about a mini clubman? Need to go look at one. I like the quirkiness of it...
I've looked inside of one before, and it didn't seem terribly useful to me. Seemed like...wait for it...a Mazda3 would be better suited to the task at hand.

I know very little about Mercedes' built after around 1995, so I'm not much help there. I know there's a balance shaft issue in the 3.5L V6s, which affected a certain run of engine numbers, but I don't know which numbers or how to tell.
If you're willing to get something that isn't very pretty, the MB R Class was available with a V8, I think it's an R 500. It's seriously roomy on the inside. Same form factor as a Venza or a Pacifica - van like, but with hinged doors rather than folding. They made a handful of R63 AMG models, too - one roared by me just last month on the highway. And I thought, other than the 10mpg that thing probably gets, what a cool car. An oversized Chrysler Pacifica that'll probably do mid 12s in the 1/4 mile.
Another alternative, if styling isn't a priority, is a Ford Taurus X, which was also sold as the Freestyle. My in laws have one, and I think it's GREAT. It's exactly the right size, and drives pretty well. Has a third row that folds down easily. They're pretty inexpensive, too, much cheaper than a comparable Flex or Edge. I told them just this weekend that if they ever sell it, I want first right of refusal on it.
It's too bad neither of us bought that R46 wagon that was for sale on the local Craigslist a couple months back. That was a real unicorn car. 5 speed, low miles, sport package, no sunroof, and vinyl upholstery. It was the ideal car for dummies like us. Unfortunately for me, the seller knew this and had it priced accordingly.

With all of that said, if you're buying something mostly for a long road trip, I'd suggest renting something. Rent a wagon or a van, do the trip, and spend your car purchasing money on something that you'll both want to drive around town.