Hey -
I can't help with the stroller or sling, but I bought a used Honda Odyssey this past year and I love it. I bought it from a person and when I sold my car, I was able to pay the Odyssey off - there are some great deals out there, so be sure to look for them. If you use Autotrader.com, you can search for very specific features that you want (under the advanced search). I searched mainly for cars under 100k miles. My Odyssey is wonderful and the part that I love the best is the sliding door so that my son can get in and out of the car by himself without me having to worry about him hitting the car next to ours in the parking lot. With the Odyssey, you just pull on the door handle and the door opens. The cup holders for the back seats are in bad locations, but my son is still in a booster seat and uses the cup holders built in to the booster. We do have the DVD player in the Odyssey, which I love. My son is 5 and can manage the headphones and remote by himself. The sliding door of the Odyssey gives you much better access to a rear facing car seat than my previous car did and so I LOVE that.
My parents bought a Dodge minivan this past year and it is nice as well. The features in it that I like are - they have shades that hide down into the door. You can lift them up and hook them on a hook on the ceiling to block out sunlight. I LOVE that feature. Also, the stow and go seats are nice.
My kids are 5 and 1. As someone said, you can get a different vehicle for just 2 kids. You don't have to have a minivan. BUT, I LOVE the extra back row for my son's friends mainly, but also for my parents. It is nice to have all of the available seating. The gas mileage is better on the minivans than on some of the larger SUVs that do have the third row seating. Definitely look beyond the dealers for a good deal though - I used Craigslist as well to search for cars.
-L.