If you are proficient, it's a simple ride. Not quite as simple as the MEI, but still straightforward. You've likely been doing some instruction since you got your CFI so that's useful. I hope it means you can relax a little and display your skill. That was the biggest difference between my initial and CFII and especially my MEI. You know this guy, you know what he likes and what he likes to fail, so there won't be too many surprises. Being prepared and calm will make it an "enjoyable ride" if there is such a thing.