We did the Grand tour and thought it was worth the money......word of warning though....if you don't like heights (like me) then think carefully before you book it LOL.
We've also done the submarine trip and I did enjoy that too however we made the mistake of booking through the Thomas Cook rep and should really have gone to Last Minute Travel as they offer the trip at a slightly cheaper price......sorry but I can't remember how much cheaper.
We also went to Fundacion Cesar Manrique which again is worth a visit.
Hope you find something
