Oh man are you in for a treat
Regarding the Aztecs, I can see them using fireworks for celebrations. The people who coined the phrase "Drunk as 400 rabbits" could probably be counted on to throw a cool party with the latest technology.
Militarily, I can see them using rockets as a seige weapon, firing them over the walls of cities from people who resisted them to cause fires and panic. The Aztec empire was a tribute empire where they relied on the economy of those they conquered to continue working, so I don't see them using an equivalent of guns to cause mass casualties and wipe out large groups of people-they just did not have the incentive.