The third Avonlea Convention is scheduled for July 27th, 28th and 29th at Black Creek Pioneer Village in Toronto. Michael Mahonen and James O'Regan are confirmed. More information may be found at the official site
Prior Avonlea Convention Information
The second Avonlea Convention took place on July 29th, 30th and 31st at Black Creek Pioneer Village in Toronto. R.H. Thompson and Rosemary Dunsmore were confirmed for appearances. Mag Ruffman and James O'Regan also confirmed.
The Avonlea Committee held the first Avonlea Convention on July 24th and 25th 2004 in Toronto at Black Creek Pioneer Village. Kevin Sullivan, actors from the show, and many fans attended. Below are links with more information, pictures, etc.
I haven't checked to see whether they are still active. Sorry!