Tips for purchasing food and drink for a talk Can people who hosted talks at your university provide some tips on purchasing food and drink for the event?

We have a visitor from another American university and I am tasked with buying "food and drink" for about an audience of 30 - 50 people. We are located relatively close to Starbucks but far away from the nearest supermarket such as Walmart. The talk will last two hours.

From what I have seen, people usually purchase donuts and coffee for these events. I have seen these coffee "crates", "barrels", (I'm not sure what to call them). 

Can anyone provide some suggestions as to where you can purchase cheap, and standard meal for these talks? I have asked people around me but they seen to have no idea, our group don't usually host visitors and the graduate students used to purchase for these talks have all graduated. 

(Again, in a North America setting)
While cookies, donuts and chocolate are always a safe bet, I have seen that fruits and vegetables are highly appreciated as well. They are really cheap, but require some work, as apples, stem cabbages, peppers ... have to be cut into pieces of finger food size. Cutting and preparing plates for 50 people takes something between 30 and 60 minutes, depending on whether you just want to serve food or have a nice presentation as well.