FWIW, I like to bring along one of those giant ziploc bags with the handle when we do wet parks; everything for the entire family (including sneakers) that should be kept dry goes in, sealed, and I can prop it on the rail and hang onto it easily. Then I fold it back up and slip it into my mini-backpack after we're done.
Note that you cannot ride Kali in bare feet, so if you wear shoes that will need to be kept dry, then you also need to bring in a pr. of flip-flops in your bag to change into while you stash your regular shoes. (None of our family wear sneakers to the parks unless the weather is really cold; we stick to supportive sport sandals meant for boating.)