I have worked as a summer camp counslor every summer for the last 5 years and I definitly agree with everyone in the tinted moisturizer with SPF. And I'd even bring along some more SPF in an oil free formula so you can keep applying it without always having to add tint. Along with some type of lip/cheek stain (Benefit Benetint is my absolute favorite), and a type of waterproof mascara (I can't live without mascara). Carry a lot of extra chapstick too. And those no water makeup wipes work pretty well too.
For your hair, I've always found that dry baby powder works the best on greasy hair, and that having a ton of headbands, ponytail holders, and bobby pins around helps. And braiding your hair (if it's long enough) can really help keep it out of your face as well as looking good.
But you might want to try unscented things to take with you too. Like moisturizer, ect. I don't know exactly how it is in California, but bugs tend to be attracted to any type of scent, even something as small as your deoderant. So it might be something to think about.
Oh, and one last little thing, you might invest in some type of sunscreen that you can put on your hair and scalp. Because have your scalp get sunburned hurts like heck and is not fun to deal with as it heals!