Should I be upset for not getting invited to the bachelorette party of my future sister in law?

I think I have a good relation with my future sister in law. I was involved in the planning of their wedding and we were asked to help with some aspects. I was not asked to be a bridesmaid which I also didn't expect, but they asked for our small kids to be ringbearer and flowers girls. We live in Europe and we wanted to leave the kids at home because of expensive flight tickets but they insisted to have the kids at the wedding. They also insisted on very specific outfits for the kids which were difficult to find. Now I just found out that she will have the bachelorette party the day before we arrive in the US and none of my sisters is invited. We expected to be part of this because we get so well together with our future sister in law. We decided not to give to much details to our brother because he thinks we are invited. We don't want him to worry about this, he should really enjoy his wedding. Is normal to feel uneasy about this or should we just get over ourselves?