Generally, you want a moderate amount of distance between the camera and the subject, in order to minimize unflattering perspective distortion. The 70-200 is great for this. If you're indoors in a smaller room, it'll be hard to get a full length shot with this lens. Put your back against the wall and do the best you can with the lens that gives you the correct framing. If you're outdoors, just stand farther away.
It's tempting to use a wider lens so you can stand close for full-length portraits, but beware of perspective distortion while doing this. For example, if you're using a wide angle lens, holding the camera at your normal standing height, shooting a full-length shot of a standing subject who's 6 feet away from you:
You're both 6 feet tall
Subject's face is 6 feet away from the camera
Subject's feet are 8.5 feet away from the camera
Subject's noggin is going to look 40% bigger than it should. Big head, tiny feet, unflattering perspective distortion.
Or, if you kneel down and shoot from waist height, their hips are going to look 20% bigger than they should. No thanks, man.
The farther away you are from the subject, the less significant this perspective distortion.