Action shots: Nikon D40 vs. Sony A100

I am looking for my first slr. I have young kids that are fast, and I am outside all the time (skiing, cycling, rock climbing, ect..) so action shots are the norm. I was set on the Nikon D50 until they stopped making it, and this is what was recommended to me. I will have a lot of family shots, as well as friends and I in the outdoors....which would be the better choice for this? My wife's cousin has a cannon, but she gets a lot of blurry pics...and she is an avid photographer so that's why i have steered clear of cannon.

I am def a point and shoot guy looking for the best quality i can get. However I am willing to learn more along the way. Any help is appreciated, thanks!:thumbsup:

I have a Sony and I'm very happy with it. Sometimes I take pictures of friends playing frisbee ultimate, and it's fine, it took me a while to learn how to anticipate the action.
But in this case I think that a USM lens (USM is for Canon, Nikon has a different name, but you know what I mean) would do a better job, since this kind of lens focus faster.
Sony doesn't have any yet, or if they do, they are maybe old Minolta G lenses (ebay and expensive). They are not going to be cheap from Nikon or Canon, but they'll focus faster. And the expensive Nikons and Canons (Nikon D200 or Canon 30D I think) supposedly they predict the focus according to the movement (I read that Sony A700 also has it or does a good job).
Here are a couple pictures that I took with the 70-210 f/4 ($180 on ebay, it's not USM).
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