I want my children to develop a relationship with my fiance, and attend our wedding
Do you know how they are feeling about your fiance?
They met her briefly but haven't spent much time with her.
It's only natural to want your children to spend time with and develop a relationship with your fiance. She'll be part of their life and much as you are so of course you would want that. I hope they end up liking her!
How am I supposed to know?
You could always ask them about how they are feeling about her. It is nice that you want them to spend some time together before the wedding.