AIBU to think if your child has chickenpox, the last thing you should do is take them to a pre-schooler birthday party?

[GrapefruitIsGross]

Totally prepared to be told I’m being a bit hysterical here.

DNephew is turning 4 and SIL is hosting a birthday party complete with bouncy castle at the weekend. We were looking forward to going and letting feral DD 20 months burn off some energy and seeing all the in-laws.

MIL let us know last night that DH’s cousin is coming, along with her two boys. The younger is about 10 and has chicken pox at the moment. MIL gave us a heads up that he will have the blisters but they’ll have crusted over by then, so won’t be contagious.

I’m very hesitant about going now- apart from how much of a nightmare it would be dealing with a toddler with chickenpox, we also have DS 11 weeks and I’m conscious how serious it can be for small babies.

AIBU to think that it’s a bit selfish to bring your chicken poxy dc to a child’s party where you know there will definitely be small kids there? Or am I being a bit paranoid?

Even if the younger one has crusted over and is no longer contagious, he might have given it to his brother who is now contagious and could spread it at the party. I would also want to know if the rest of the CP childs family had already had the CP and so couldnt be brewing it/contagious.

CP comes out in crops. My friend had it last year and was developing new crops over a period of nearly 2 weeks. She therefore had a mixture of crusted over and new blisters at the same time. All the blisters have to be crusted over and no sign of new ones in order to be non contagious.

It's ridiculous and selfish. Absolutely don't go. Get your 20mo vaccinated though. Babies over one can be vaccinated at boots for £75 x2 which I know is a fair amount but worth it imo.
I went to a wedding last year, whilst 7 months pregnant, where someone had brought their pox ridden ds who was apparently not contagious, I only found out when he was standing 3 feet away from me so that I could see his clearly fresh blisters, I was horrified at the parents, but more so at the b&g who knew, but didn't even give me the heads up so I could stay home (dh was best man so not just a random guest who they wouldn't think of) They had a baby of their own so clearly knew the risks. I left and had to go to the hospital (non maternity ward to be safe) so they could check bloods overnight for immunity, luckily I had it. I was so upset I refuse to have anything to do with them now and DH has cooled the friendship.
I just think you should never trust people's 'oh but they've scabbed over' as they can't be 100% sure and often just say it so they can attend. Make sure SIL warns all guests, as it's really unfair otherwise. Perhaps the thought of doing this and the possibility of no one wanting to attend will encourage her to ask the chicken pox child and their sibling, who will no doubt be contagious, to stay home.

How can they be so sure that the kid will be crusty by the weekend? Even if you've dealt with it before, surely every case is different. And that's before you consider the risk of the sibling/parents having it but not knowing and spreading it around. It's infectious before the spots appear.

If the party was another week away I'd understand the attitude better, but it just seems a bit selfish.