OP, I think there’s a lot of people jumping on bandwagon and you’ve had an unbelievably hard time.
I understand the stress of an emergency review. It is (thankfully) many years since I had to attend hostile SEND meeting about my child, but it still brings me out in a cold sweat just thinking about it.
I’m sure you’re doing your best for all your dc. It sounds like horrible timing, but it is just one day (of timing clashes - I know full well the rest of it carries on!)
Take 5 minutes. Have a cup of tea, breathe, and then make a plan for the day - what will make attending the nativity easier for you? (I think you know you have to attend, really). Is there anyone you could ask to look after your younger dc (wheresbouts are you - I’ll do it, seriously), or for the review time. Otherwise, the usual - snacks, diversions (favourite program on a tablet/phone plus headphones?) - seriously, whatever it takes.
You can do this. Make sure you plan a nice evening (for you all) afterwards - hot choc, easy tea, Christmas film to watch together, whatever you all enjoy.
And I hope the review goes as well as it can. I have my dd’s annual review tomorrow, and even though it’s not an emergency hostile review, it’s still going to be tough, they always are. I hope you can take 5 minutes for yourself amongst all this too.