The only point of contention I see is that you are making the buttons disappear, effectively preventing him from clicking something "wrong". Telling him what to press next is ok, had plenty of FaceRoller type addons do that in the past. Making it so he can't press something wrong is another story. FaceRoller said push this button next, but it never took away your other buttons preventing you from ignoring the addon and making what the addon considers a mistake (in practice it may be the correct decision to deviate).
This is a new area in addon development. Instead of playing the game for you by doing the "right" thing all the time, we are now developing addons which instead are designed to prevent you from doing the "wrong" thing (such as the addon designed to prevent clicking on Atramedes' shields early). Blizzard hasn't really addressed this new school of thought in addon development yet. So "is it ok?" I don't know yet. Personally I disagree with it though. This type of addon however would only effect a clicker, because even if the button is hidden, the keybind is still active. So large scale application of such methods isn't likely in the near future.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.