I don't think so.
The Americans with Disabilities Act requires reasonable accommodations, not total.
I do not think asking a person (or their guardian) who has a serious life threatening illness to provide documentation that they do not pose a risk to other patrons as an unreasonable accommodation.
The child in the pool would be in close contact with other patrons and as the pool owner stated he did not know the potential for transmittal from a 2 year puking on another patron (not unreasonable to assume a sick child might puke in a pool). I do not believe this is a strong case for violation of the American with Disabilities Act.
And permitting a family to use a public facility is a totally reasonable accommodation. Any court in the United States will agree.
The child in the pool would be in close contact with other patrons and as the pool owner stated he did not know the potential for transmittal from a 2 year puking on another patron (not unreasonable to assume a sick child might puke in a pool).
Ignorance of the law is not a defense. I'm not sure how often children puke on one another in this fellow's establishment, but as I'm sure you know, vomit cannot transmit HIV.
I do not believe this is a strong case for violation of the American with Disabilities Act.
That's fair. Plenty of lawyers will disagree with you, and I believe there's actually a pretty hefty amount of case law to back them up on that.