Awesome! Lucky that you're making the trip on the 9th, I've always wanted to go to one of the organized naturist hikes but haven't been able to. And this time I'm actually taking a group up Mt Baldy that day haha. So the wife and I are playing hooky from work and going Tuesday the 12th. Fingers crossed she enjoys it and gets hooked like I did (I do a lot of Free Hiking in the Angeles National when I cant make it to Deep Creek).
Haven't done Mt. Wilson yet but want to, my favorite day hike so far is San Gorgonio. It's an ass kicker as well! And I did Mt. Whitney last summer as an overnight, which needless to say was amazing!
Since you're camping yes the water filter is key, going for the day I just bring my hydration bladder and a gatorade (and some beer if I wanna carry it haha); oh yeah and if you get there early and snag 2 trees bring a hammock! I'm gonna bring a bigger pack when my wife and I go so she doesn't have to carry anything but a water bottle, I want her to have an amazing experience.