No I couldn't afford that much BUT I still don't understand why you or anyone cares. I also don't see why you feel it's worth mentioning that she has 9 kids and doesn't work? Her business and finances, noone elses. Maybe she invited everyone so noone was left out.
Nicer holidays? That insinuates that you already have holidays and would perhaps upgrade if money was available. Well, we don't have holidays but choose to spend a bit more at Christmas and birthdays. Sounds like you do the opposite: have holidays and spend a bit less at Christmas.
I guess my point is, we all have luxuries on some level. Yes there are starving people in the world but those who choose to spend more at Christmas shouldn't be made to feel bad. Do you feel guilty for having your holidays? Probably not as you've worked hard to be able to do that. I don't think I've ever heard someone being bersted for hsbing a break away yet people think it's ok to judge someone for spending £xx on their kids at Christmas.
By the way, £15 per child for soft play party? Ludicrous. It only costs a fiver here for a session and the food isn't a tenners worth. They certainly know how to make their money at these places don't they!