Single moms and dads who have begun to date often wonder, When should I introduce my kids? That's an excellent question. Ideally, though, I think you should grapple with this issue before you even begin dating.
On one hand, enjoying a casual dating or social life apart from your kids is healthy. They certainly don't need to know every detail or set about appraising someone's long-term prospects before you've even had a chance to decide about a potential relationship for yourself. But on the other hand, you do need to talk with your children about your basic life goals, and share how your vision of the future you hope to create will affect them.
For example, if you know you'd like to get married at some point in the future, clue your kids in to that before you go bringing someone home to meet them. In other words, let them get used to the idea of even recognizing you as a "social" being before you expect them to accept or even tolerate the inclusion of a significant other in your life.
For an explanation of how to go about having this conversation with your kids, and how to actually introduce them to your new boyfriend or girlfriend when the time is right, read the article How to Introduce Children in a Serious Dating Relationship.