Hi RMJJ, and welcome--or as they like to say around here:
Would you like to say more about the relationship and how it ended?
10 years is a long time. What did you do to process the relationship after it was over?
What was it like for you, being out of contact with your children? How has it been reuniting? It sounds like you feel things are going well with them, but then... .
The reason I am writing this is that though the two eldest accept the fact that I do not want to see or have any kind of contact with their mother, it does not make life easier.
what is "it"? The fact that you don't want contact with their mother? Is it your relationship with your older two kids that is stressed, or is it YOUR LIFE independent of the kids that feels stressed?
The scene you describe in the supermarket gives me the sense that you have a lot of unresolved conflict. Maybe... .anger is a way of offsetting the feeling of wanting to help her?
Telling more of your story might be a way to bring out some more details about your emotions.