Alcohol? Yes Or No

I am having a small summer wedding with around 100 close family and friends. Since it will be taking place on a Sunday afternoon I didn`t want any alcohol. My fiance however, wants at least beer at the reception, this is the only thing he has asked for so I want to give it to him but we don`t have the budget for a bar or even a bar tender and I am strongly opposed to having a keg at my wedding. My parents are also afraid of being held responsible for people who get too drunk. What should I do?