You're a father now. What you want doesn't matter anymore, it's all about your child. We have an 05 SR5 V8 as well, and an 11 month old baby boy. We live in pothole hell "chicago", and I can see where your wife is coming from. But, in terms of an SUV in general, you'd be hard pressed to find a smoother riding vehicle than the 4runner in that segment. No way a "true" SUV like a 4runner is going to ride like a minivan. She wants a Sienna. If she's the one that'll be spending most of the time taking care of your child, then I suggest you listen to her. Because in a few months, when you realize that your child was crying all night long and you didn't hear a thing, and she was up with him/her and didn't wake you to help, you'll be FAR happier driving that Sienna then the other way around. These are words of wisdom, from one new father to another.
We moved to Chicago from Carolina in Feb, and had the 4runner loaded down. Yes, the extra weight smoothed it out "we have the tow package". The vehicle felt "at home" with the extra weight in the back.
We love our 4runner as our family wagon. I have an 01' GS430 for my manhood though, which does the trick for cheap.