How to get a group all in focus

[wulf]

Find a online Depth of Field calculator and run some numbers. The two primary factors are the aperture and the distance from the subjects. Once you've got some numbers, try some test shots - a bunch of inanimate objects will be perfect as they won't get bored with you making adjustments.

Another possibility is that your lens may tend to be softer towards the edges, hence Allan's question about what lens is very relevant. For example, my 70-300mm lens is quite soft and subject to chromatic aberration at the 300mm end so I find that it is often better to back off to about 200mm than to try and zoom in all the way. Online reviews might help but, again, you can test this yourself by taking a carefully worked out series of pictures.

Wulf