Knowing that you've recently started a photography business, I also thought you meant posed group shots, like at weddings or family reunions,etc..
I dunno...I still think that groups of people photographed with very short focal lengths tend to look awful...big,looming foreground people, and then the people just four feet farther away look half the size...just dull,and uninteresting,and not compelling to see people photographed with ultra-wide-angle focal lengths.
When I got started in photography, a 35mm was considered a wide-angle lens. A 28mm was _the_ standard wide-angle. A few people had the very wide 24mm lenses. A 20mm was rare. The 17mm focal length was called "ultra-wide".
Personally, I dislike the corner distortion of the 24mm focal length. I sold my 20mm because I so,so seldom wanted to ever use it. For anything.
I think Destin might have the right idea, on the Tamron 15-30mm. I do not think that relying on just one, single focal length ultra-wide makes much sense for landscapes; it's too restrictive, and forces your hand a lot. A zoom makes more sense, for framing and composing in better ways,more easily. With a prime, you virtually always have to move the camera position to get variety of composition. A 15-30mm has a LOT of focal length options, from ultra-wide to wide-angle, whereas an 11-16mm is just an ultra-wide, and has no semi-selective top focal length setting options.
If you look at zooms of the past 20 years or more, we've had 17-35mm f/2.8 models and Canon has has several 16-35mm f/2.8 models; Sigma and Tamron and Tokina have followed suit; there's a reason for this.