[Stattick]

Stop being an author. There is no "wrong" or "right". There is "fun" or "not fun". To hell with what the published adventure says, do what is fun for you and the group. A gm's job is to faciliate fun. Granted, what's fun varies from group to group.

So, if it would be more fun for you and the players, then let there be magical stairs that slide out of the wall when they trigger the hidden switch. If that wouldn't be fun for you and the players for some reason, then don't. If they are having fun, then you're doing a good job, enjoy it. If they are not having fun, then do something different, to bring the fun back.