In a word, yes...but the bank will exchange your Canadian dollars to American dollars at an unfavourable exchange rate plus commission before they exchange into Belize dollars, once again at an unfavourable rate plus commission.
If you insist on using travelers cheques, get them in US dollars and most likely you'll be able to cash them when you make purchases.
That said, my advice as a fellow Canadian is, get enough US cash to get through the first day and then use the many ATMs as needed.