As Andrew said, the 55-250 works well for portraiture in the 55-100 range. Take a head and shoulders photo at 18, 35, and 55 megapixels, then at 70 and 100 megapixels. Examine the differences in face characteristics, backdrops, and subject isolation between pictures. You'll see that most of them are fairly similar at 18MP but more detailed at 100MP.
Beyond that, I'd say it's up to your personal preference as to whether you want a wide angle or not. The tradeoff is quality vs. size. A wider lens allows you to get closer which can be useful for getting more into a room or scene. It also means that you see more of your background than with a narrower lens. However, this also means that there's more of the picture that isn't your main subject that needs to be kept clear of distractions.
If you plan to take lots of pictures of one scene or event, then a wide angle is better. If you're only planning on taking a few shots per subject, then a normal lens will do just fine.
I think the 35mm focal length is wonderful for portraits IF you want to incorporate the surroundings, and it makes for a much prettier "picture" in my opinion. I started getting tired of the conventional 85mm portrait "heads" a few years ago. It seemed that every photographer was using them, so I decided to try something different.
The first thing you'll notice when photographing people is that they are not super-small on camera. Most cameras can shoot images up to about 9 inches tall by 6 inches wide, which is plenty big enough to include most people's heads. You won't be able to fit everyone, but you'll definitely get a good look at those beautiful eyes!
The second thing that will strike you right away when photographing people is that there are many more options than with landscapes. There are foreground, midground, and background elements that work together to create an image that has depth and dimensionality. In fact, the more varied your subject matter, the better photographer you will be.
Finally, when photographing people you should definitely try to connect with them on some level. This could be as simple as looking them in the eye or nodding your head, but even subtle gestures can help bring out natural emotions in the subject that you might not otherwise see.
If you want to capture excellent, professional-looking portrait photography, you should invest in a big aperture prime lens or two, as well as a large aperture zoom lens, such as a 24-70mm f/2.8 or a 70-200mm f/2.8. These lenses are great for getting close-up and wide-angle photos.
For more distant subjects or if you just want to have some fun, you can use a small aperture fisheye lens. These lenses produce very distorted images, but they're fun to use and create unique photographs.
Finally, if you want to shoot video with your photos, the best option is to buy a camera with integrated autofocus and image stabilization systems. This will allow you to focus accurately and prevent blurry videos due to shaky hands.
Here are some other considerations when choosing your lens: cost, size, and feature set. If you only need to take occasional photos of family members, then any standard lens from any manufacturer should be sufficient. However, if you plan to take photos for a living, or if you enjoy experimenting with different techniques, then buying multiple lenses might be worth it. A big lens that covers a wide range of focal lengths can help you achieve special effects such as shallow depth of field or wide angles.
Photography for portraits The Canon 24-70mm lens allows you to photograph both big group pictures and close-up individual poses without changing lenses. A lens with a bit more reach than the 70mm maximum length would be great for tight headshots.
Portraits The Canon 24-70mm lens is useful because it gives you a wide range of focal lengths, allowing you to shoot several different types of photographs with one lens. For example, you can use this lens to take both landscape and seascape photos as well as indoor and outdoor portraits.
Landscapes The 70mm focal length is very common for landscapes because it gives you a moderate amount of overlap between shots, helping to avoid repetitive patterns in your image sequence. You can get much longer focal lengths if you need to, but they become difficult to handle due to weight and size limitations. The 24-70mm range is very convenient because it provides enough coverage for most situations while still being light and compact.
Seascapes There are two main types of photographs taken at sea: action shots and scenery snaps. The Canon 24-70mm lens is useful because it allows you to capture both kinds of photo without having to change lenses. This saves time and makes sure you don't miss any important scenes during long exposure times required for action shots.