The simple, common-sense answer is no, a small amount of sumac wood (such as could be accidentally consumed with sumac tea) is not poisonous for human consumption. We can conclude this from the fact that A) normal sumac tea preparation methods can include some of the wood, and B) people don't get sick from sumac tea prepared by these methods.
People have ...
A bit more methodical approach to IDing this plant:
Opposite leaves + a corymb of multiple dark-colored, round drupes is very indicative of the genus Viburnum.
If we check BONAP and Ontario Trees & shrubs, we can see that only a handful of Viburnum species are found in Ontario.
From Ontario Trees & shrubs:
Viburnum alnifolium (Hobblebush)