I would definitely have water, soda (coke, diet, ginger ale and maybe root beer depending on your guests) and maybe iced tea or lemonade. You could also offer coffee and tea if your guests are into that.
I agree with PP on their soda ideas, maybe toss in some sprite. I see you are having a June wedding so Iced Tea and lemonade is also a great idea! I would definitely take a look on pinterest. There are great ideas how to make sodas stations (saw an "crush" station. adorable!) or non alcoholic drink stations.
What does your venue and/or caterer offer in your package? I ask because our venue includes the catering and bar, and we can just purchase the food package (without the bar), and it includes a variety of soda, water, iced tea, hot tea and coffee.
So, you may want to check first, to see what, if anything is included. Then you'll have a better idea of what more you may want to add.