It sounds like part of the Nickelodeon series "The Third Eye", which would make it somewhat difficult to track down, since it was taken from several other BBC mini-series'.
If I recollect proper, the good wizard's name was Roscoe, who had made this maze or labyrinth that could transport people to different parts of time, & the three kids where looking for a stone called The Nidas.
Oops! Just double checked.
Into the Labyrinth
http://imdb.com/title/tt0081877/A couple of other titles from The Third Eye were;
The Haunting of Cassie Palmer
http://imdb.com/title/tt0245629/Children of the Stones
http://imdb.com/title/tt0075491/Under the Mountain
http://imdb.com/title/tt0202769/