I had this earlier this year. My husband went to huge lengths to arrange a surprise birthday night out for me with my closest friends, including booking a 5 hotel all paid for for those coming from far away to stay, then on the Sunday a party for our daughter turning 3. Bearing in mind that I hadn’t celebrated my birthday in 8 years, and I mean at all, after the last time I tried crashed and burned in a similar manner, and also I was a month away from giving birth to our second child, had a horrible time with our first, and DH was really keen to give me a lovely positive memory before the sht potentially hit the fan again. They all knew this.
Well, they all cancelled bar two, leading to the night out being cancelled completely. Thankfully we’d invited several other people to the party they we know but aren’t as close to with similar aged children, and also my husband’s close friends came, so it was still a lovely event, as yours will be too.
I don’t understand why people think it’s ok to act like this, never have, never will, but it’s certainly a salutary lesson in who you can rely on. For the sake of your one year old I would do your best to rise above it, as they don’t mind who’s there, but will enjoy a day of being spoiled by those who love them, and I promise it will be a positive memory all the same.