It's only the Americans that are anal about people going to Cuba. Cubans don't discriminate and will welcome Americans with open arms. Visa to Cuba is a tourist card, so regardless of what passport you bear, it will not be stamped or have anything glued in it. US cash is accepted, however heavy penalty is imposed on exchange from US dollars so you're much better off exchanging for Canadian dollars before arriving to Cuba.
http://www.cubatourism.ca/usa-cuba/u...uba-americans/
and
http://www.cubatourism.ca/usa-cuba/t...-problems-usa/