...but I'm also a poor college student so I would like for this camera to last me a couple years at least before I upgrade. So what I want to know is, which camera should I get?
I would like to be able to photograph a variety of things such as: children, landscape/wildlife and action sports (i.e. motocross and kids sporting games).
You do not mention lenses. Getting good lenses will cost much more than a camera body. I'd go with a Rebel refurb from the Canon store and a couple of good lenses. You will keep and use good lenses for many years, but bodies come and go.
You will be wasting your money to buy a 7D and then get a cheapo lens.
Spokane said it well... the most common mistake you can make is putting all your money in a camera body, and slapping a cheap lens on it.
Here are some non-intuitive things to know about DSLRs:
It's all about the lens:
~90% of your image quality is the lens. You can put a great lens on a 5yr-old entry-level camera body and take amazing photos. You can put a cheap lens on the newest pro body and take mediocre photos.
Lenses don't depreciate... bodies do.
In 2006, I bought a Canon 30D body for $1600, and a 50mm 1.4 lens for $300. 5 years later, the body is selling on ebay for $250, and the 50mm lens is selling used for $300. In our world of iPod and laptop economics, that probably doesn't make sense... but that's the way it works. Over a 5-year horizon, it's as if you borrow your lenses and rent bodies.
When you look for lenses, aperture is more important than zoom.
If you look at two lenses:
Canon EF-S 18-55mm f/3.5-5.6 vs.
Canon EF-S 17-55mm f/2.8 IS
The 2nd number is really important... since this is your first DLSR, I'm going to assume this is new to you. If it's not, I apologize. The lower the f/# (sometimes written 1:#), generally, the better images you will produce. Low f/# lenses are called 'Fast Lenses' - but speed is only part of the story. Have you seen photographs that look almost 3D, with things in the background blurring out? That effect requires a large aperture (small f/#, or 'fast lens'). The problem is that that number also is directly correlated with the diameter of the lens... which requires more glass... and glass is heavy and expensive. So unfortunately better Image Quality (IQ), bigger, heavier, and more expensive are all on the same side of the scale.
With that, I strongly recommend picking one excellent lens, and good lenses are ~$1000.
Then, take whatever money is left in your budget and buy a used body off eBay.
In 4 years, your $1000 lens will still be worth $1000. You can give the camera body to the neighbor kid to learn and buy a 7D off ebay for $500. Once your student loans are paid off, then go get a whiz bang body.
Finally, You said you want to take children, action sports, wildlife, and landscapes.
Unfortunately those are all different lenses.
Pick one place to start. Below are some suggestions... not the best, but generally good bang for your buck.
Good Generic lens - Landscape, Children:
Canon 17-55 f/2.8
Decent substitute: Tamron 17-50 f/2.8 <I haven't used this one... so do some more research
Excellent for Children and portraits
Excellent for outdoor Action Sports and Wildlife
70-200 f/4 IS
All you need is a rock-solid tripod and a good alarm clock... the lens and bodies are far less important.
Finally, get a good book... DSLR for Dummies is a pretty good start.