The Giant's Rib Raid (early April) and Raid The Hammer (early Nov.) are GHO's annual 25K
team adventure runs. These events attract a nice mix of adventure racers, orienteers and trail runners at the start and end of each season. There are racers of all levels, with a very high level of competition near the top of the pack.
There is also the Navstock camping weekend of orienteering every June if you prefer individual events, more time to socialize, and fun for the kids. This year the Canadian national team trials will take place at NavStock, so the level of competition will be especially high.
If you're keen on snow, you can't always depend on having it for the Giant's Rib Raid like we did this year, so I'd suggest the new 3-hour Snowshoe Raid (solo or pairs, Score-O) in February. Check out
http://www.dontgetlost.ca as the schedule evolves.