No, not if he has asked this of you...it's not treating him like a child. It's ensuring he has the info in a manner that works for him. That's actually a good thing for you both. He's just done you a favor and clued you into how to communicate more effectively with him.
As Cobra said there are differeng "learning styles". I often have to teach classes where I work with adults...some are Audible learners, some are Visual (like myself), some are tactile....many are a combination of these things.
My husband tends to be a Visual/Tactile learner...so if there's something I want him to do for me (specifically in the bedroom) I show him what I want by guiding him with his own hand (or whatever body part is necessary). That way he remembers the next time what it is that I like specifically. If I were to simply say do this, with that, then do this....he'd never remember it. It's just not him. I would though, but I'm an Audio/Visual learner.
If he's asked you to write down the steps, just do it. Communicating things you want him to understand isn't much different than teaching someone information in a classroom environment. Do what works for him to ensure you get the information across...it doesn't haveto be how you would get it.
