I don’t think anyone is being horrible. Really, what would be horrible is bringing a potentially infectious child, who really doesn’t need to be there because you have childcare in the form of your partner, to a space that you know is going to be full of medically vulnerable people.
I know it’s disappointing, I had all my scans by myself for DS because covid. It’s shit. I really do get it but unfortunately this is just how it goes sometimes when you have 2 kids and no wider family to step in. Get used to it as it’ll be the first of many. DS was sick a couple of week’s ago so had to miss nursery, I stayed home with him and DH went on his own to DD’s school play. Of course I was gutted to miss it but you don’t take a child that is excluded from school/nursery because they’re infectious out and about with you even if they’re ’mostly over it’. It would be incredibly selfish. Consider this your first adjustment to being a family of 4!
Also even if your 7YO was in great health and it was just the school holidays you still can’t do it. If they’re too young to stay home by themselves, they’re also too young to sit by themselves in a hospital waiting room. The medical staff aren’t babysitters and it would be downright negligent to just abandon a kid of only 7 years old in a public place even just for ‘5 minutes’, which it’s unlikely to be tbh, probably more like 15. Just no.
I hope you reconsider and I hope all goes well with your scan. It may not have been what you wanted to hear but the responses you’ve received are all fair and reasonable. Even the one about the sick bucket because let’s face it, it is a possibility because she’s had a bug and better in a bucket/bag than down her, on the floor, splattering on whoever has the misfortune to be close by.