The airline you're on makes a huge difference. SW is (generally) all on one concourse. Delta on the other hand spans three+ concourses. Although large, Atlanta is very easy to get around. Each concourse is a long building and they run parallel to each other. In the middle of each concourse is escalators/elevators to take you to the walkways/plane train below. You can walk between concourses (and there's moving walkways) or take the plane train (picture a monorail).
About a week before your trip, start watching
https://flightaware.com/. Put in your flight numbers for the day you're watching. You should see a trend of what gates they arrive/depart from. If not specific gates, at least what concourse. This is no guarantee you'll use the same gates, but a pretty good idea.
Download your airline's app. After your plane lands and gets off the runway (while taxiing), fire up your phone, go to the app, put in your flight information (both flights) and it should show what gates you're using. When you get off the plane, head immediately to your next gate. Do not stop for food, do not stop for a bathroom break, do not collect $200. Once you get to your next gate, see how much time you have before boarding. Only then go to the bathroom/get food.
You also don't say the ages/walking ability of your party. If you have a baby and need to wait for a stroller, that affects your time. If you have someone that uses a walker or cane or wheelchair, that affects your time.
48 minutes in Atl is tight but doable. One time I changed planes (including changing concourses) in 5 minutes. BUT, it was just me, both gates were close to the central connectors, and I caught the plane train perfect.