Totally depends on your environment whether you need to lock them up in the coop at night.
I have raccoons and hawks, so I have to take careful precautions for my mommas and babies, however, if they can sleep safely in the dog crates in the coop run without fear of predator, that works really well.
Yes, babies this young often have trouble following up a coop run, especially if it is somewhat steep. That is why I generally just put a plastic air craft dog crate at the bottom and let momma take up residence inside the enclosed run but outside the coop....IF I don't have predator problems.
I now have a wooden broody hutch that I lock at night after a coon cleaned me out of some hens last winter. I let momma and babes out each morning and lock at night. I have a lower run but still that was a problem for babes until about 2 weeks of age. You then have a choice...pick babes up each night or arrange so that you don't have to do that by having a large enough coop to accommodate.
I've done it both ways. Now I have a large enough coop for the first 2 weeks of age, then let momma and babes out in an enclosed run from which momma takes them back into the broody coop at night. At which point I lock and bolt the door (lousy coons).
But all said...if it is safe in the run, then simply set the crates inside the run and let mommas go into the crates and night with free access to the run during the day. In time, both mommas (usually by 2 weeks as the babes are flying like sparrows then) will take them into the main coop...or you can encourage that by taking crates away.
LofMc