As I understand it (tho' I haven't checked before posting this) - the normal flu season mainly kills off the elderly or others who have underlying health problems. The swine flu, on the other hand, is more often fatal to children and young adults - who were otherwise healthy before getting it.
If your kids have had doses of flu this year, there may be some immunity there. However as far as I know there is no risk associated with getting the jab, so I would get them vaccinated*. The momentary discomfort of a needle in the arm shouldn't weigh against protection against a potentially fatal illness (if that is what you meant - apologies if I have misinterpreted this bit).
The risk to others from carriers is not just about not them getting the current version of swine flu, but that the more there is of it about, the greater the chance of it mutating into something even nastier (I think!).
*as I haven't any kids, this is hypothetical, and you may think I am less qualified to offer an opinion...