Ok, so I don't know that you can expect much change with the loss of the CN as he's not really getting any less daytime sleep, it's just more consolidated, iyswim.
If you'd rather have the long morning nap, then I'd start pushing the first A time longer as previously mentioned until it lengthens to 1.5-2hr. Then, you can decide how you want to proceed with the second nap. It doesn't need to be cut at this point, but is good to keep in mind sleep totals, as if there's too much day sleep the morning wake-up won't get later even with a later BT.
Katherine made a great point about DST as well. Are you in the northern hemisphere?