Is the ramp smooth or does it have some sort of foot holds? It does seem like it could be a little too steep for chicks' little legs. But, the mother will take care not to leave them to be beaten on by other birds. The other hens might break up, but sometimes it takes a little help...
Just like any other Mom, a hen with a brood will travel as she sees fit. I would watch to make sure she is caring for them, as sometimes, very rarely in my experience, a broody hen will abandon her chicks. They will follow her and do mostly what she tells them to, both outside and inside. If...