WA for a group shot? who told you you need a wide angle lens for that. My last photo I did at a wedding I shot yesterday was the rest of those that stayed. cant remember how many. but around 20. have to check the pictures. but I didnt use a wide angle lens at all. in fact, for proper aesthetics and correct perspectives a wa lens is not what you want to use.
not only that but during the wedding, the parents wanted pics with their friends from work and I was so tight in space that only there I had to use my 28-70 AFS at 28mm. but my technique is bring the people from behind. I dont like rows where you basically see people in the front looking like they have two heads on their bodies. and move back and zoom in.
I cant recommend a WA lens for group shots. I use a tamron 17-35 2.8-4 and use it for 2 things. 1, when I have NO choice because the dance floor is so tight and crowded (weddings here are 300+ people at least) and 2 for photos of the venue. tables, chuppa. but just a few. I never took it out once for group shot. I will do all I can before Ill shoot people with anything wider than 28mm. thats my widest. and those who do those stair picture...it wont happen everywhere that youll have stairs appear magically. thats just a luck thing for the situation. and even then I wouldnt use a WA.
but since you said this
I want to get her a new wide angle lens that doesn't make people look short and fat like umpa lumpas for the group shots.
I will chuckle (cause its cute) but also nod and say oh geez. no wide angle lens from 50 onwards makes people look good. you should learn about aesthetics and focal lengths that makes people look good. those focal lengths are simply not aesthetically pleasing for portraits. you can shoot full body shots 24-35mm but it isnt aesthetic. you will see those who are towards the edge will look fatter than they are. not only that, but if you shoot 2 rows or more, the ones in the back will look tiny and far from those closer to the lens. also, let me say it once. there is no wa lens, none, that you will shoot past 24mm (and even 24mm is a fine line) and they wont look umpa lumpa. the wa pulls their faces and stretches anyone being dowards the edges of the corner or edge of the frame. thats the laws of lenses. the people in the middle will look fine (not really..but..) but those towards the edge will look fatter.
when I shoot groups of people, I try never to do 2 or more rows of people. I bring everyone to the sides, making a straight line and go back and shoot. anything from 35 onward depending how much space I have to work with.
when I did the family formals yesterday, I moved back and shot everyone (mother/father/3 brothers/2 grandparents/bride&groom) at around 85mm. perfect aesthetics, straight and they look amazing. i would never shove a wa in peoples faces. my technique has the background compressed right behind them and its nice and blurry. theres a clear seperation between the background to them. with wide angle anything in the background will be in focus. distracting or not.