Slip slap slop seek slide.
Just an umbrella won't protect you from UV rays, let alone if you spend a lot of time outdoors and the umbrella doesn't have a UPF. Even then, you'll have rays reflecting from surfaces. Do you wear long clothes? Do they have a UPF? And where do you live? (Rhetorical question, I don't need to know that of course)
If you are worried about chemicals, try mineral sunscreens. Non nano. They look and perform like shit but this is literally just zinc oxide sitting on top of your skin, reflecting the rays back like a mirror. Nothing is penetrating your skin, nothing is turning photons into heat. Zinc oxide is a compound you can get in a baby cream and a lot of pharmaceutical creams and it is reducing inflammation.
I like the umbrella, don't get me wrong, but depending on what exactly you do it might just be not enough. I'm worried it provides you with a false sense of security. Trust me, Japanese people don't rely on their umbrellas only.
Well, this is the worse scenario. If he goes down the "FASD route" it will be rather easy to debunk. An "increased risk" route will be much vaguer, more believable, and harder to disprove.
This might also go down the route of "if it wasn't safe in the womb we should think twice about giving it to my baby who has a high fever" resulting in brain damage and death. (For the record: Fever is good, but high fever in babies is dangerous.)
This, then, adds up to "I didn't give my baby tylenol when it had a fever, then it was hospitalized, they gave tylenol after all, now the kid has XYZ, it was the tylenol".