If the terms of your event allow it, it is nice to be able to offer those who are really keen the chance to get their own Go set and book. Someone who has invested a few pounds in one of these is more likely to follow up with the game.
Firstly you will need a stock of sets and books. The BGA bookseller or Pentangle will usually supply these on a sale or return basis but there might be a cost for delivery or return. Bear in mind how much you can carry to the venue from station or car park.
If you do decide to sell, then the best Go sets are the 13x13 ones with 9x9 on the back. The two types are the BGA-designed A3 laminates and the ones with plywood boards in pizza boxes, which are nicer to play on but more bulky. You should avoid 19x19 sets as this would be a big commitment for a student to make and, as you know, small boards are better to learn on.
You may also supply a beginners book at a reasonable price, such as that by Charles Matthews or that by Neil Moffatt (both British Go players), but do not expect to sell as many as the sets.
The BGA can supply you with a supply of such sets and books to sell, heavily discounted and on a sale or return basis. You should contact the bookseller  in good time to discuss your requirements.
Also you will need appropriate amounts of change and somewhere to keep it. You will find a lot of people will not have cash on them, but at least you can show them what they can buy and direct them to Pentangle to buy on line.