I do this a lot, offering trips over Central London, which is quite a draw.
I do not meet the requirements of the AIC, as I have six seats, so I write to the CAA on each occasion for permission. I point out that, although I fail to meet one criterion, I exceed nearly all the others.
They reply with permission very efficiently by return of post.
It really is no big deal. The only difficulty that arises is that you don't know the date of the flight before the raffle, so you put up the prize without certain knowledge that the CAA will grant permission. Luckily this has never proved a problem so far.
Timothy