Commemorative $1 or a $2 notes might sound like a neat idea, but if they are intended for circulation, they will flop. They will end up in drawers, much like the mint's unsuccessful attempt to promote the 50ยข coin with a high mintage for-circulation commemorative edition back in 2002.
If commemorative $1 or $2 notes are produced as NCLT, I can see them being sold for way above face value in commemorative holders, much like the lasting impressions sets, that few collectors will buy, and almost no non-collecting Canadians will ever see.
A $5 note would be the best for visibility and utility, just like the $1 was back in 1967.
I agree, the $1 and $2 notes will flop because they will not circulate. It needs to be one of the current denominations, ideally the $5. The BOC could release existing $5 designs with a small commemorative overprint, similarly to what is being planned for the $20 commemorative notes this fall. These notes should not require any changes to the software in ATMs or any other banknote-reading equipment, they will still stand out and, most importantly, they will circulate, giving everyone a chance to find one of these notes for face value.