hi,
I would say 8 w and a few days if those are your reasons for going. because then you'll be 8 weeks pregnant but in your 9th week.
can I ask you where you got your "chance of miscarriage" stats from?
i've got a scan booked for 7weeks 6 days next friday and to see that if we see a heartbeat and everything normal again (last scan was 5 weeks 5 days and all was normal) then the chances of miscarriage being around 2% would be a big relief!