I use the same full sized backpack that I use at Disney, a Boba Fett lounge fly. but do put less stuff in it, so it can squash down to fit in lockers. I've tried fanny packs, but I'd rather have more room, and have all the usual stuff I like to bring to the parks. However, this last trip, did have to have my son get a second locker to hold the refillable mug, water bottles/gatorade, and we opted to put the phones in his too. No big deal at all to get lockers, except had to wait a few mins at Velocicoaster one busy time, but they held the whole line, VC lockers are located w/in the queue, and love that, so can keep phones until then.
Reading through the thread tho, and my look at replacing, getting a more waterproof bag for future trips