As soon as the first ticket was "revoked", the cost should be refunded. However, it sounds like this was done ("sit on our money for four months"). An argument could be made for the interest on the line of credit and possibly the change fee if charged. If the credit card does not deal with it for you, small claims seems to be the most fruitful approach.
AC doesn't care about the reason for travelling so the family reunion, etc. is interesting to CBC but has no relevance to what they owe.