how to tell family that--> wanna be a CMT?...gonna be a hard one! Any tips?

It all depends if they are against you joining or want you to join something else ultimately its your choice. Tell them its what you want to do, if your set on it then tell them the reasons why, some parents get worried about certain jobs as they think its too close to the front line etc. Just reinforce the fact that everyone is trained to do what they do so there will be no need to panic but the parents instinct is to do that anyway so best bet is to talk to them first and then tell them. its not always easy but parents are often more understanding than you think.