It actually all depends on which vampire stories you are reading. There have been some vampires that have had kids (I just re-read the entire "Preacher" graphic novels, and Cassidy, the Irish hard-drinking vampire, states he has several), but in general the bite of a vampire replaces sex. In Chelsea Quinn Yarborough's Count St. Germain stories male vampires are impotent (again the bite replaces sex), probably for the reasons mentioned above, but female ones are not, so most likely could have kids. Of course the crappy Van Helsing movie (cool effects, horrible plot) had Dracula creating vampire eggs of all things.
One thing to remember, before receiving the Blood Kiss and becoming a vampire, there are no restrictions - so use that in your fluff. The vamp passed the kiss down to his natural children - making an entire immortal vampire family (think "Lost Boys").