If it's only an extra 15-30 mins of extra A time before the next E, I would just keep it very low-key and non-stimulating. It is very common, and should sort itself out as he's able to stay awake longer before naps. Just keep in mind that he might need his next nap 45 mins -1 hr from the original awake time, making there very little A time after the next E. You might end up with an extra catnap in the evening to get him through until bedtime.
What does his day currently look like?
