Good thoughts for AKP this morning. Let us know how it goes 
Glad you're feeling better Cheeky and good news that you've got your scan booked in, albeit a few weeks away.
I second suggestions above for not drinking Macauley. This makes me feel massively self conscious, maybe its because no-one would go out for a drink and not... well, have a drink in my circle of friends. Rounds are awkward if that's likely. Try to avoid getting into that if you can.
Whatsername I don't know much about HCG levels but calling the midwife might be a good idea. If you explain why you're extra-anxious, I would hope for some sympathy? I hope it goes well with your parents later.
The when to scan / tell people thing is a proper quandary. I didn't have an early scan but now like others I will so wish I had if its not good news on Wednesday. Equally, 12 weeks is supposed to be the time after which it's not unreasonable to relax. Would I have spent the last few weeks any differently having had a scan? We haven't told anyone at all and don't plan to yet. All being well, we have a big family holiday booked for early June. I can't see how I'd be able to get through that without them knowing but ideally I'd wait til the 20 week scan. If there is bad news on Wednesday, I can't see that I'll be sharing it with anyone IRL. I think I must have some kind of emotional deficiency because I have always been this way - the idea of someone recognising some failure on my part, the pity that that engenders is utterly intolerable to me. I am quite envious of those who feel able to seek support.
There is another factor in this for me which is the unplanned nature of this pregnancy, and the fact that we will be the first in our circles of friends to go down this road. I am not expecting particularly positive reactions on the friends side so I'm putting that off for additional reasons. Sorry, all that is so not in the spirit of this thread. I shall try to be more positive.