It seems reasonable and prudent to go through decontamination after this sort of thing, but if the worker had just gone home to their family soaking wet without changing, there would still have been close enough to zero risk to anyone (again, cleaning up and making sure this is the case is a very reasonable thing to do).

This sort of place is safe enough to bring your kid into without significant precautions (I got to do this as a kid—it was really cool). The biggest risk by far is drowning.

Relevant XKCD: https://what-if.xkcd.com/29/