Sniffing wine is definitely allowed! :)
I have some tips on hiding that you're not drinking.
Get one weak white wine spritzer. Drink that slowly, getting it topped up every so often with more soda. Keep the glass all night and just keep going!
Of course this only works at an event where you can avoid rounds or are paying for them yourself. My friend did this at an event we were at recently and i had absolutely no idea until she told me at the end of the evening (she was just doing it not to get drunk as had to work).
Another tip is to accept the drink, and simply not drink it. Take small sips, and then chuck it away at the first opportunity.
Not sure how you'll get away with a whole night of clubbing though!
The exhaustion may pass. IIRC, it's the progesterone causing it. Usually your period arrives and stops the rise of progesterone, but now you have higher levels and it's making you tired. You might not feel this way in three weeks. Having said that, I wouldn't fancy staying out late and staying on a floor right now anyway!
Could you say you were on anti-biotics? Ill? Change the plans?
We went to a festival last weekend and I simply told my friends as I'm pretty open with them. If we have to face a tragedy then I'll tell them that too. I know most people wait till 12 weeks but you don't have to.