You need to make absolute sure that your kids are ready for the introduction. I would even keep the person secret until you know the kids are ready because this is a huge deal to them. Kids react differently, even among both their parents. By this I mean that some will accept the father finding a new love but not the mother and vice versa.
When you're sure they're ready, move super slowly. Maybe make it aware that you are going on dates, then involve your kid(s) on some while making them the center of attention. Just don't force them on the outings if they are not into it. It can be very, very difficult to adapt to a new person in their parent's life and a lot of kids have a tough time letting go of the fact that moomy and daddy won't make up.