It should be noted that this is the opinion of some obscure, self appointed group with no particular qualifications.
You notice they don't say he is the best father, just a father of the year. If it were somehow possible to determine who was the best father, I don't believe that Clinton would make the the top one million.
You are right that this is some obscure self-appointed organization. And that is exactly why they are doing this. Its a way to generate donations, period. They did not analyze whether Clinton is the best father — his daughter is an adult and he has no kids so even if he did not have his other issues, this wouldn’t make sense. Charities do this all the time — give an award to a famous person to glom onto their fame to make money.