My opinion is that a lot of different flooring changes break up the house and make it seem smaller (and cheaper). Is it possible you will sell this house someday, or are you there for life? What are the ages of your family? Do you have little kids? Even if you plan to never leave, if someone becomes wheelchair bound, you may want to move someday. I think it's always good to think of possible resale in making big ticket choices.
If I had any idea I might sell, I would go with one flooring from entry on through. My personal preference is wood. Tile is hard, but durable. Travertine is a very soft stone, can chip, and needs to be sealed. It's a hard surface to stand on in a kitchen- and to fall down on, on the stairs. ;) Of your choices, I would probably go with a good quality vinyl the whole way through. Or think about cork, it's pleasant to stand on and fall on. LOL.