I thought of that at first too, but then I thought
-that the chick who made him a vampire was taking pleasure in the fact that he couldn't be with his family anymore (since she couldn't be with her husband) and that she probably wouldn't want him to know what to do to make others vampires so that he would be unhappy too
-that he wouldn't be able to make the kids vampires as they were so young and then you have an Interview With a Vampire thing where it just causes a whole lot of trouble.
Also, wasn't one of the kids still a baby/toddler? How do you make a baby drink daddy's blood? And since the baby would always be the same age, they are looking and lifetimes and lifetimes of diaper duty!