In this example, the kind of irony which is used is <em>verbal irony</em>. In verbal irony, the speaker says one thing but means another. Verbal irony is used in a variety of circumstances. Clearly what the mother says is not what she really means, it is not likely to see a ten-year-old driving a car. Using this irony, she adds humor to what she says.
I think it's verbal irony because verbal irony implies something different from what a person actually says. This kind of irony usually occurs in conversation.
Huck reacts by not being able to speak or breathe because he is so scared. I think he is starting to realize that life isn't forever and life can be quickly ended by other people, so you have to be careful with what kind of situations you put yourself in and who you surround yourself with.
