Questions about probabilities and other selves

[Blue]

I have a question and I'm not sure how to word it, but I'll do my best... Say I went out to lunch at a restaurant with two friends of mine. Later, for whatever reason, I decide I want to alter the past, and change the memory of this outing to the three of us going shopping, instead. I understand that in doing this, I will be removing the probability of the lunch outing from my past and replacing it with the probability of us going shopping. Therefore, a probable self of me and probable selves of my two friends would be the individuals doing the shopping because it's an entirely new probability event.

That being said, I am wondering this -- If I decide instead to NOT alter my past, and keep the memory of the three of us going out to lunch, every time I recall this lunch outing, it will be altered slightly, because every time you remember something, it changes in some way. Does this mean every time I remember this lunch outing memory, I and my two friends are exchanging with probable selves in this event, because the past is altering in some slight way? What if I begin to remember something new about this lunch outing, such as my two friends arguing over something? Would they exchange with probable selves because they are acting differently, even though the event of the three of us eating lunch is the same?

I hope this wasn't confusing and that someone can answer these questions for me because I am very curious about this