Seeing those show dates I would prefer Renfrew for March 4th or 5th.
It's a decent hunting show in an accessible town, held early enough for newbies to get plenty of info and gear prior to the season starting.
Added bonus is that Renfrew has The Rocky Mountain House... Which is by far one of THE BEST restaurants in Ontario, and has no problem accommodating large groups. As well as the Gourleys Hunting & Fishing store.
IF a hunting show is NOT key to this gathering, then a meeting in either Richmond (That Hunting Store) or North Gower (The Old Co-op) would work well also.