Your set up is really nice. I added a white tarp for $19.99 that is 11.9 x 9 I got at Home Depot (online only) that I put over one side of my run due to the strong cold winds we get from that side of the run in the winter to protect my flock.....lets the light in using a white tarp. We had such high winds a few weeks before we put the tarp on, my chicks were blown across the run...thus the tarp.
I built a coop 4 x 6 and a run 12 x 6 and after all my 4 chicks and 3 ducks have now gotten to two months old, I found the run area was not large enough. I just added two 10x10 connecting kennels to give them the needed run space. The four chicks sleep in the coop, so the space there is fine. The ducks sleep in nest boxes in the run area under the raised coop and that is fine. However, when they are all up and running, so to speak, there is minimal running since that 12 x 6 space contains a small pool for the ducks, food/water area, and nest boxes for the ducks, so the true run space is more like 8 x6 which was too small. When one first gets new chicks or ducklings, the space looks great. But, when they get older and larger, then a possible resizing needs to be considered, as in my case it did.
Here are a few pics of my set up for some ideas you may, or may not, want to use or think about. To give the chicks and ducklings a way into the new kennels I added a wooden tunnel for them to access the kennels. If it quits raining for a few days, I need to paint it white like the coop/kennel.
https://www.backyardchickens.com/forum/uploads/106085_cooprunkennel.jpg
https://www.backyardchickens.com/forum/uploads/106085_run_encl_w_tarp.jpg
https://www.backyardchickens.com/forum/uploads/106085_new_kennels.jpg
https://www.backyardchickens.com/forum/uploads/106085_looking_into_tunnel.jpg
https://www.backyardchickens.com/forum/uploads/106085_wood_tunnel_outside.jpg
https://www.backyardchickens.com/forum/uploads/106085_top_of_tunnel.jpg
Good luck with your new chicks...they are so entertaining and so much fun to have. I just love 'em all to pieces. Suggestion...you may want to add hardware cloth to the bottom three feet of your present fencing, all the way around, to keep raccoons from pulling your chicks through the fence and decapitating them.