The 7D has a built in flash so there's little need to have another one in the bag. The two lenses have full frame equivalent fields of view of 38mm and 64mm respectively. There isn't a gigantic difference - one is a bit shorter than normal and the other a bit longer than normal. But there's enough difference to carry both.
Here are the two fields of view on the 7D. The normally smooth Hudson River has a different look doe to the passing of a New York State Marine Highway tugboat and barge just before I made the exposures.
|EF 24mm f/2.8 STM (38mm eq.)
|EF 40mm f/2.8 STM (64mm eq.)
The rest of these are made with the 24mm lens at and above Lock E2 on the canal in Waterford.
I'm going to include this kit in the pancake project as the concept is the same. The 24mm is almost the same field of view and the 40mm is the same lens.