Due to the lack of predators in the country I live in, mine don't have a ramp to their coop, so I have no experience with this. Do your ducks have a ramp to their coop? If they can do it, chances are ducklings can. When my hens hatch babies (even ducklings) the hens will often sleep in the nesting box (which does have a ramp) so I guess the mothers will teach them.
Ducklings are quite fall resistant, (one of my duckies was caught by a hawk once and dropped, he was X-rayed at the vet and fortunately the only issue he had was punctures from the hawks claws, no broken bones at all) so I doubt falling from the ramp would be an issue if it did happen. Usually the mothers teach them everything they need to know.
One thing I noticed was when the mothers got out of the 'protective stage' the ducklings would be pecked sometimes by the other hens, it was never anything lethal, but the other hens seem to know that the ducklings are invaders of sorts. So just look out for aggressive behavior.