Define what “leave at 7:40” means
For one adult, 7:40 may mean walking out the door. For another, it means the car is moving or the bus is arriving. Choose the observable event that matters. If the bus departs at 7:40 and the stop takes seven minutes to reach, the household cannot still be looking for shoes at 7:35.
Build the last ten minutes in physical order
For a car departure at 7:40, a trial might set coats and bags ready by 7:32, door locked by 7:35, and everyone at the car by 7:38. Use the real path from home to vehicle and include anything that must be carried or checked. The last adult out should know who has the keys.
Change the bottleneck you actually see
Try the plan on a normal morning and note where time disappears. If shoes repeatedly take longer than expected, move that task earlier rather than moving every alarm. Keep the exact departure time visible to whoever handles the last check.
If the car leaves late because a bag is packed at 7:36, prepare that bag the previous evening. If the walk to the stop routinely takes twelve minutes, update the departure plan instead of telling everyone to hurry through an impossible seven-minute walk. Recheck the timing after a few ordinary departures, not only after an unusual delay.