The balloons have weights to avoid them from being let go and flying off. That becomes a hazard when they eventually land elsewhere and deflate, potentially in waterways, like other plastics.
The horses are rotated through and have appropriate resting days. These horses are shoed for the work they are doing and some of the best cared for animals. These aren’t circus animals - lets cut the bull on “we need to end using the horses in shows”. Horses have been used as work animals for centuries, they are beautiful animals, and some people never get a chance to even see one. To come to Walt Disney Workd as a child and see Merida riding a real horse must be an amazing experience for a child. Clearly this was a freak, sad situation, and as others have said, kudos to all of the cast involved in the situation!