I'll try but probably fail to keep the details vague...
We have a 2yo DD. We only see DH's aunt and uncle 2-3 times a year, but they dote on DD and there are always excessive photos/exclaimations of how good she is etc. When visiting them nearly six months ago, DH's aunt and uncle told us they were planning a big birthday party this December, save the date. Fine.
Mil has heard about various arrangements as they have been made since then, and the option of booking a room at the venue was discussed and taken up by pil and DH and I. Fine.
When visiting the aunt and uncle again with pil a couple of months ago, there was further group discussion about this party (which has turned into a bit of a beast) and we found out it is to be black tie, dinner the works. , but fine.
An official invite arrived a few weeks ago, along with a Christmas card (!) with a note saying how they are so pleased we can join them and look forward to seeing us in December. The envelope was addressed to Mr & Mrs Doodle, the card to me DH and DD, and the printed invite had no names... (Can you tell where this is going yet!?)
I bought DD a beautiful dress, which I told mil about, who speaks to the aunt and/or uncle maybe weekly.
When visiting them last week, mil told them that is the venue could supply a highchair, great, if not, DD is fine on a chair. She was met by absolutely incredulous rant from the aunt (her sil) about why would we even think about bringing a child to a party like this. None of her friends would presume to bring their children to an adult event. She genuinely couldn't understand what gave us the impresion that DD was invited. Basically, poor mil got in the neck, they stuck to their guns about DD and then smoothed it over for the sake of family harmony.
Now poor mil has had to tell DH and I. Now, I am a bit cross that it has come to this and we've already booked a room. I do understand people want child-free events sometimes (although I wouldn't make that choice), and if it were clear from the beginning (or any point until firm arrangements were made), I would be happy to arrange for DD to stay with my mum. But now it feels as if she has been uninvited, and I can't help being a bit miffed. DH is cross (as I would be if it were my side of the family), but we have agreed he has to go so as not to upset his mum. Apparently if we can find someone to look after her, she can stay in the hotel room and come for breakfast the next day. I have said a firm no to that suggestion, it's not fair to disrupt her routine for no reason. I am minded to send DH with his parents and stay with DD and send them my apologies and best wishes. I am not really upset that they have excluded her, because she is too young to understand, I understand people want child-free events, and at least it's not my family being a bit bonkers! But I am irritated at how they've gone about it, and that aunt was apparently very judgemental that DH and I don't leave her with a babysitter every week and go and 'socialise'. And I feel for DH.
We made opposite assumptions, but were we wrong to assume what we did? Should we suck it up and leave DD with my mum? If DD were older and therefore disappointed I would definitely stay with her (and take her somewhere to wear her new dress), should I do that anyway? I'd like the excuse to get out of this to be honest. Don't get me started on the 'gift list'. Grrrrr, rant over.