Family pregnancy announcement

Hi
I’m looking for some advice. My fiancé and I are planning a September wedding in France mainly with family and some of our friends. His family will be travelling over from Canada.
We have found a venue and are about to book our date and send save the dates out for September. We’ve made it know since our engagement over the past few months to our friends and family that we are looking at September.
This week my brother and SIL called to say they are expecting their first child, and they wanted to call to let me know straight away because they will be due in September and know we are wedding planning for that time.
Myself and fiancé are now in a dilemma as to what to do.We can’t easily pull it earlier because of giving F&F enough time with save the dates. Also if we push it back it will likely be into spring of 2025, 6 months later, as we really don’t want a winter wedding. An added complication is my grandma is my last grandparent and she is elderly. Pushing it back is an added risk that she might not be here or there are family complications later down the line with that side of things. By contrast my brother got married 2 years ago and had both our grandparents there. It means so much to me having my grandma there, which is why we are looking to get married this year.
I honestly have no idea what to do. Please let me know your thoughts and what you would do in this situation.