I concur with [b]singleshot[/b].
If you cannot refund the tickets, why not go anyway? The Kennedy Space Center is pretty fascinating all by itself. Take one of the tours that tool around the launch pads and VAB. And the Imax films ... awesome! I myself could spend an hour or so just wandering around the Rocket Garden.
It's a shame you cannot make the launch. On a clear day/night I can see the launch from way over here on the west coast in Pinellas.
As for the tickets, IIRC they are good for that specific mission. So if you have tickets for STS-107 or STS-112 for example, they should be good on whatever launch date they do come up with. Obviously if they pick a date in which you cannot make it then it's a no-go.
Finally, if you ultimately cannot use the tickets, see if they are transferable. Perhaps you have friends or family in the area that could use them. I saw a night launch once with a VIP car pass and I cannot recall if it had anyone's name on it or not. Of course, those were pre-terror days when they wouldn't have been too concerned anyways.
LL