i have the luxury of a stroller to be our “catch all” for the big stuff (sunscreen, water bottles, snacks, small bag with medicines like tylenol and moleskin, princess costumes to change into at a moments notice, etc). i leave that stuff in the stroller while we are on rides, and haven’t ever had a problem
i usually bring a small backpack (it’s 1/3 of the size of a regular one) or a sling type of bag that holds my wallet, camera and video camera, tissues, lip balm/lipstick, etc. and just take it on the rides with us - i haven’t had a problem finding a spot to stick it on rides at all! oh - i do put the camera/video camera in waterproof holders inside the bag, just in case!
next years trip though, DD is really too old for a stroller (or so we are telling her, she isn’t buying it) - so i’m not sure what we’ll do. i think i’ll still bring it, just in case - she and her sister both get tired and since we are park commandos, it may be best to take it just in case!