How many weeks do you plan to keep them in that? I wouldn't keep them in there for more than another week or so, they look almost fully feathered and like they are running out of room. If it's more than a week or so, I'd give them twice that amount of room (zip tie two kennels together if you can - I removed one door from a 2-door kennel and connected it to another same size kennel - it works well - I clean out through both of the other doors that open to the outside.
For keeping the shavings in, use old feed bags and zip tie them in place underneath the tray. Or cardboard that works too. Either way, have it go half to 2/3 up the sides, to keep airflow through the top and top sides. I used a roll of housewrap, but old feedbags work just as well - it's the same material.
ETA - if you use cardboard or housewrap, you don't need the chicken wire to keep them inside.
