We have had good luck exchanging CAD to Pesos at the ScotiaBank on Avenida Espa?a but they really aren't very familiar with Canadian bills. Last time we went in with a few hundred dollars in $50 dollar bills, the teller walked away and was showing the bills to the people at the desks with a look of confusion on her face. Finally they called me over and asked why one of the bills was different. I turned it over and showed them they were all the same.... Enough said....LOL. I would recommend them if you really needed to bring CAD as we have gotten a reasonable rate there, but I usually just use my TD debit card at an ATM INSIDE a bank. Never use an ATM on the street.
I've used most of the banks in the Bavaro/Punta Cana area as well as in Higuey and La Romana with no problems other than having TD cut it off because I forgot to go to my bank ahead of time to make sure they knew I would be using my card in the D.R. I phoned them from the bank parking lot, got it straightened out and was able to use it again just fine. Before I go I also have TD reset my maximum withdrawl limits to much lower than I have for use at home. I can always use a credit card for a large purchase or plane ticket if needed. The account I have does not charge me for using my card outside of Canada, so I only pay the D.R. Bank fees which do vary from bank to bank.
Just make sure to advise your bank of your travel banking plans and make sure they enter it into your file properly before you leave and you should be fine.
ETA: You lose money if you convert CAD to US at home then US to DOP once you arrive.