Hello Melanie
We did a similar campaign, and can give some advice. You need to be very careful not to use language like BUY A SEAT as it is not tax deductible via your Building Fund. I can send you our collateral if you wish but need your email. Here is the campaign on our website – we used trybooking as well.
https://www.trinity.sa.edu.au/community/foundation/donate-to-the-foundation
Regards
Kay Fyfe