I have thought about it and the pain that Kevin has inflicted on you is so recent and your newfound self worth so fresh that I am going to suggest you not let Kevin come this weekend.
If you feel that him visiting now is only going to set you back (and I believe it will) tell him no, you are not ready to see him now.
I have never read about much interaction between him and the children anyway so I don't necessarily think preventing him from seeing them THIS time is cruel on your part.
While it will never be okay for you to keep him from the kids unless he is a serious danger to them, at this stage in your situation, my advice would be to do just that. Unless having them be at your Mom's house or your Sister's house for a couple of hours where he can visit them without you present is an option, I say tell him not to come this time.
You have been hit too hard, repeatedly by his selfish, outright vicious and adulterous behavior. In 5 minutes he can tear down what you have worked for weeks to build and I just don't think he deserves that opportunity right now.
I think you need to continue on this path you are on, for your sake and for the kids sakes. Kevin removed himself from the equation and the work that has to be done towards a reconciliation is mostly on his part. He is not worth you falling back into the same dysfunctional thought patterns you are only now starting to grow out of.
Soon though, you will be even stronger and then you will be ready to see him and he won't be as much of a threat to your feelings of self-worth & self-confidence.
IMO, it's just not a risk I think you should take.
And he hasn't even earned the right to ask you to.
