If it's only 2 feet off the floor just make sure you have a good layer of bedding like pine shavings on the floor and they will just jump down when the hen calls them. Mine do it all the time, even higher nest. As long as the floor is soft they will be okay. If you can't let yourself let them jump down when your hen gets off the nest just grab the babies and put them on the floor.
The chicks should be okay with the flock. There might be a bit pecking and grumbling, but in a day or two they will get use to the new little things running around. I have 32 standard to large size hens, one bantam size hen and two large Brahma Roos and when I have a hen hatch eggs she hatches them with the flock and they are out running around by day 3 at the longest. Right now my banty hen hatched 7 standard size chicks on the 26th of March, she took them out with the flock on day 3.
let them out, you hen will know what to do. If your hen is real low in the pecking order I would watch the other hens more then the roos. Just keep an eye on them, but I wouldn't intervine too much.