There are a few misconceptions in this thread not least is the belief that attendance donations are eligible for Gift Aid – except in very restricted cases they are not, see:
Chapter 3.37 Membership subscriptions
3.37.1 There’s a statutory requirement, under Gift Aid, for payments to be gifts. This means that payments that are made to acquire goods or services aren’t eligible for Gift Aid. However, there are rules within the Gift Aid legislation that allow charities to provide donors with token benefits, within specified limits, in recognition of their gifts.
3.37.2 Most membership subscriptions aren’t gifts, they’re made to gain access to the facilities and services provided by the charity.
Also the belief that donors must sign a Gift Aid Declaration before their donation is eligible for Gift Aid – that is true for donations >£30, once a Charity has qualified the GASDS [Gift Aid Small Donations Scheme] allows the recovery of eligible donations of £30 or less even if the donor has not signed a declaration and has not paid tax.