Occasionally I'll have one of DD2's classmates before school, as it helps with his parents' working situation.
I have 4 DCs who obviously will have to be cautious over their eating habits for life. Genes. 
Therefore we have only cereals that are not excessively sugary for breakfast.
This child moans about what is on offer at my house. So he then asks for augar to be added to weetabix, which I would rather not, but if DS is not in the room he can have some discreetly, as the girls understand my rationale, but DS is only 4 and I would rather not have this eating style visible to him.
So, AIBU to request politely that he doesn't add sugar when ChaoticBoy is around?