I'm going to go against the consensus and caution you against getting a DSLR. I find this forum jumps on the DSLR boat too often and too quickly. Straight from your op, you admit you don't know what a lens does. That is troubling to me, and I can't recommend a DSLR if you don't know basic photography.
Now, I'm not bashing DSLRs. I'm suggesting that you seriously consider what you are willing to sacrifice for photographing your stepson. Yes, sacrifice is the correct verb. A DSLR is much more powerful and flexible than a P&S... if you know what you are doing. In the hands of a common photographer, a DSLR is no better than a P&S and can actually be more constraining.
Ask yourself these questions.
1) Are you willing to spend the time to learn photography? Almost all DSLRs come with an automatic mode, but if you hoping to emulate magazine photographs using that mode, forget about it. The real power of a DSLR lies in the manual controls, and that takes time and experimentation to learn. Additionally, learning the camera's features is just a small part of the battle; the real difficult part is acquiring an eye for photographs. That may take a lifetime.
2) How much money can you spend on this? No matter how you cut it, DSLRs are not cheap. Worse, the camera body itself is often the most affordable part of the entire package. The lenses and other accessories will cost you. Before you deny that you will need to upgrade, let's examine your needs. You want to take photographs of your stepson playing sports. The kit Canon lens has a zoom factor of 3x. Even at the highest zoom, your photos will contain more of the field than your stepson. Now you have to upgrade. Maybe get a 55-200 zoom the previous posters recommended. To protect your lens, you should get some filters. And a bag for all your equipment. You'll discover the built in flash isn't that powerful, so maybe it's time to get a new flash. Everything costs $$$, and before you know it... (my next point)
3) Are you comfortable carrying around a huge brick of a camera? DSLRs are big. Their accessories just add to the bulk. Lugging everything around is a pain. Forget about sliding your camera into your pocket and heading out. Now you are concerned with keeping a second eye on your stuff. If you lose or someone takes your stuff, that's a big chunk of $$$ gone.
Hopefully, I haven't drove you away from photography yet. If you are willing to put up with the above, by all means get a DSLR. Read no further, it will be a great investment. Seriously, just stop here.
However, if you are just a casual photographer, someone who just want some photographs but none of the complexity, avoid DSLRs. Luckily, the camera makers recognized your market segment a while ago and began to manufacture cameras for casual photographers who want to a more powerful P&S/ simpler DSLR. They created the mega-zoom P&S cameras. The sheer amount of built-in features is amazing, but they are straightforward enough to allow you to just take pictures without the BS.
Let's see what a Panasonic Lumix DMC-FZ35 has:
1) Cost is $350
2) 18x zoom, 27 - 486mm (35mm equiv.) and image stabilized. This is more zoom than a 200mm on the Canon.
3) Macro ability for close objects like flowers
4) Many different continuous shooting modes, but the standard is 2-3 fps for 5 images
5) HD movie recording. Forget about having this on an entry level DSLR.
6) Grab it and go.
7) And a multifold of other features that only a serious photographer would care about.
This review, even though it's a bit old, will give you a pretty good insight into megazooms.
http://www.dpreview.com/reviews/Q109superzoomgroup/
Before anyone flames me, if you compare images from a DSLR and a megazoom at a pixel level, a DSLR would be undeniably better. But, I doubt you would be able to tell a quality difference from a printed 4x6 photo. The only difference is:
(kit DSLR) Here is Timmy's school. If you look very hard in this corner, that little dot is Timmy.
(megazoom) This is a photo of Timmy tackl... well, I'll just let the photo speak for itself.