Well, if they are shiny, they've probably been sealed already. I'd suggest getting some leather dye, from Tandy leather, if there is one in your area and doing a spot check somewhere that wouldn't be very noticeable. Either your dye will bead up on the surface or sink it. If it beads up, you're SOL. Even if it sinks in the best you could hope for is a very dark brown since the leather is already black. It would be like trying to dye black hair brown.
Spray painting would give more opaque coverage, but as you said, it probably will end up cracking and peeling.