This is such an important question. You show your love for your children by being mindful of the possible impact of the meeting on them. I don’t have enough information to give you concrete advice. But here are a few general guidelines.
It’s crucial that parents only introduce a new partner when they are as certain as possible that the new love is going to become a permanent part of the family. The children have already experienced the loss of their original family. Kids are affected by that fact, whether the divorce is an amicable parting of the ways or the result of bitter fighting. It’s unfair to set them up for another loss.
Five months may seem like a long time to you, but it really isn’t for making such an important, lifelong decision. Yes, it would be easier to spend time together if the kids were included but working around their needs for awhile longer may pay off big later. Ask yourself whose needs you are meeting by introducing everyone to each other now. Are the kids’ needs first in your thinking? They should be.
Make sure you and your partner are on the same page about parenting, especially whether she has any authority. You need to have some ground rules established before she meets the children. Children, being children, will want to figure out what the rules are. Often the way they find out is by breaking some rules to see what happens. Be prepared for that.
In an ideal world, the kids’ mother should be supportive of someone new coming into your life. Do what you can to make that happen. Too often, children find themselves in a bind. If they like the new partner, they sense that they are letting their mother down. If they don’t like the new partner, they are letting you down. Your ex doesn’t need to be your partner’s new best friend but it does make life much easier for the kids if the adults can be adult about each of the parents moving on.
My best advice is this: Be patient. You have plenty of time. It’s more important to do things right than to do them in a hurry.
I wish you well.