Babysitting an 18 mo. old at a church; what do I need to bring?

The girl I'm babysitting, Chloe, is very well-contained, although her attention span is just that of her age. Since it's at a church, all they have are some old, used toys in the nursery, although I don't feel they'll provide much towards Chloe and her spunky personality. I know of a spot in the church where there's balloons, bubbles, and sidewalk chalk so we could go outside and play with those. But if it rains, there's some books to read and such. However, I need to know if I need to talk some snacks, etc. I'm already bringing some band-aids, and some child-friendly CDs to listen to if she happens to get bored. Other than that, I don't know what else to bring. Any pointers?