I don't think solving the puzzles is a problem, as long as it is clear to the player which actions can be done and as long as it's limited to one level (so you don't need to pull some switch in another scene in order to progress).

It becomes difficult if there are hidden action the player does not know of (e.g. looking below some sort of carpet in oder to find a key hidden there).

Still I think there should be some challenge to the riddles.