You've gotten great advice so far, and I don't want to overload, but did want to add a few thoughts.
Before heading a bit north to work for NOC, I grew up in the Atlanta area... going to middle and high school in Suwanee. You can't beat Gwinnett County Schools... ranked high in the nation (well above the Ga state average). Living in Suwanee, Lawrenceville or Buford will put you close to a lot of nice suburban amenities. While you will deal with surface street traffic, you can avoid work commute highway traffic (name of the game for surviving in ATL) and spend your free time playing outdoors vs. in your car.
But if you preferred to live a little further out, I would suggest Flowery Branch or Gainesville (both are a fairly quick and light traffic commute to Suwanee on 985S), or even Hamilton Mill/Braselton areas (also easy commute… but down I-85S). Those are still pretty suburban… and not “far” out thanks to urban sprawl. You would have a fairly easy commute to Suwanee from all those places… only hitting highway traffic sometimes and only as you get within a few miles.
An easy drive from all those are flatwater paddling options - Lake Lanier, Chattahoochee River and Fort Yargo State Park; mtn biking/trail running options – Gainesville College, Chicopee Woods in Gainesville (amazing!), and Ft Yargo. Looking for whitewater paddling, head to the Nantahala (2.5 hrs from Suwanee), Chattooga (~2 hrs), Ocoee (~2.5 hrs), and US Whitewater Center in Charlotte (~3 hrs). If you’re up for monster whitewater… check out the Cheoah (limited release) about 3.5 hrs from ATL too. Like someone else mentioned, definitely check out the very active and great ATL Whitewater club.
Once you are settled, definitely come visit us at the Nantahala Outdoor Center in Bryson City, NC. It’s a paddlers paradise up here!
Good luck with the move. Colorado mountains may be higher and the weather cooler, but our Appalachians are older, wise and storied. You’ll have a great time exploring!
-Lauren @ NOC