The Brown School cards are available at Mr. Crepe (as the post above mentioned) for $10 cash. While it clearly doesn't make sense for you to buy them for all your students, perhaps you could tell them about it in advance and suggest they bring $10 cash with them if they think they might be interested, and then stop off at Mr. Crepe towards the end of your tour (so that they'll have had a chance to check out some of the places the discounts are for) and give whoever wants to buy one a chance to.