DD doesn't tend to eat much at brekkie time either - she has it with her dad at 7ish before he goes to work, but at most, it's half a piece of toast or half a weetbix. I then give her morning tea around 9.45-10, and she'll eat either 2bits of raisin toast, or a weetbix with fruit - so at least double what she eats for brekkie. I just think that she's obviously not as hungry at brekkie time, and make up for it at morning tea.
So maybe giving a bigger morning tea is the way to go. I know you said he's at creche 4 mornings, but maybe if you had a chat with them and mentioned that because he doesn't have much of a brekkie, could he have more at morning tea. I'm sure their flexible. Could you maybe change your morning routine, and leave having breakfast till just before leaving the house - that way he might be hungrier?