Sample Children Model Portfolio / setcard.
Model : Sansan Mangalindan
As you described yourself to be a newbie, and inquiring about a Canon-mount dream lens, chances are you're using an APS-C Canon body (1000D, 600D, 60D, 7D, more like 1000D?), meaning your camera body has a 1.6 crop sensor as opposed to the pro/prosumer 5D/1D series, which have the fullframe sensors.
If so, I suggest you stick with Canon lenses; the 24-70 is designed as the workhorse midrange zoom lens for the fullframe bodies, with the ideal wide angle of 24mm for landscape shots and the ideal zoom range of 70mm for portrait shots. Mounted on an APS-C body however, this lens becomes a 38mm-112mm (24mm x 1.6crop factor, and 70mm x 1.6 crop factor), giving you longer reach but you'll find you'll be coming up short on the wide end. Explore the 17-55mm 2.8; some call this the "hidden L lens", now this is the workhorse midrange zoom lens for the crop bodies. I myself prefer to use the 15-85mm; even though this lens doesn't have constant aperture of 2.8 like the 24-70 and 17-55, my 50D and 550D compensate this by handling shots better at higher ISO than the older body models, and with a sweet zoom range of 24-136mm fullframe equivalent, I have a lens that can handle landscapes, portraits and the occasional "stalker/voyeur" shots.
If, however, you are one lucky bastard to have the 5D or 1D series body models.