Hi. I have leather couches, too, and although my cats don't intentionally scratch them they have made a lot of marks with their back claws when running and chasing each other. I recommend keeping their nails trimmed at all times, and maybe using soft paws until you can train them. Mine have gotten better since they've gotten older (they're only 1 and 3 years old), but they still occasionally freak out while chasing each other and jump onto the furniture and dig in with those back claws.

If you do get any scratches, immediately take a damp washcloth or finger and buff, buff, buff! I've found that rubbing the scratches with a damp finger really helps to minimize them.

Good luck! Hopefully you won't have any problems.