Hammer drills can be used like regular drills if you disable the hammer action. The hammering part is only for use when drilling through concrete/masonry, not while drilling wood. They're heavier and have a higher amp draw than a non-hammer drill. Unless you know you're going to need to drill concrete/masonry, I'd stick with a regular cordless drill to start with.

Impact drivers are for driving screws, bolts, nuts and the like. You can use it like a regular drill (not hammer drill) if you buy the appropriate bits, but it's not that great at the task of making holes.

My recommendation would be to go to your local home center and pick up a pair of cordless ones. One drill, one impact driver, and at least one battery. Ingco, DeWalt, Makita are all great brands. Whichever you choose, realize that you're going to be stuck with that brand because all the other cordless tools you get will need to have interchangeable batteries. I use the Ingco's myself and have been very pleased with them, still going strong on the original batteries after 3 years of non-professional use.

Others may disagree, but that's my suggestion. Good luck!