I agree with what several people have said here. As the daughter of divorced parents, I can say that waiting until you're 100% sure of the person staying in your life is the best decision for the children. I saw both sides. My mom waited to introduce my brother and I to her second husband, whereas my dad introduced us to his new girlfriend almost right away. We grew attached to both her & her family, so when they separated later, it did a lot of emotional damage - we didn't just lose her, but her family. My dad was just being selfish in thrusting us into a relationship with his girlfriend - it was easier for him, so he just did it. My mom's choice of action was a lot more considerate of the well-being of my brother and I.
And as the one on the outside of the family, you have no right to decide whether its time to meet the children. It's the mother's choice alone. And hint - you'll win brownie points by being patient and understanding about it.