I can do a group shot of 12 persons sitting side by side easily, at the 24mm end of my 24-70mm f/2.8 mounted on my FF 5DMkII, standing about 3m-4m away.
If you use a 1.6x crop camera, the 24mm focal length would be effectively 38.4mm. My opinion is, at this focal length I will need to stand further back to accommodate the same 12 seated persons.
Can certainly be used, these two lenses 24-70mm and 24-205mm. Just with some inconvenience.
Most would interpret it as wedding shots.
But 3 people also group shots, army bmt passing out also group shot leh.
Anyway, if camera to subject distance is too close together, be careful the unavoidable optical distortion
at the two sides of the pictures. The wider the lens, (with the same subject image size) the more distorted it will be at the sides.