Well it is not ideal to eat right before bed, but I long ago made my peace with it, because they have to eat sometime and they have to get enough sleep.
Do you mean he rarely eats meat, fruits and veggies at all, or just not late at night? One thing I figured out long ago is how to hide veges in other things so the kids get enough. We do veges as sides as well, but the hidden veges really help.
Our coaches have talked to the boys about the importance of proper nutrition for athletes. It helps.
My older son who is 13 now has the latest practice we have ever dealt with and is home about 9, after starting at 5PM. We live less than 10 minutes from the gym, so car eating does not make sense for us. I used to feed my kids dinner before evening practices, but they both complained of feeling sluggish at practice. So now they have a good snack before practice and eat dinner after, and dinner is whatever I made everyone for dinner, leftover. And yes for older DS that means he eats a full meal (although not a large meal, he is not a big eater at any meal) and goes right to bed. So far it has not caused any issues, he sleeps fine, etc.
I think carbs are fine for right before bed, but ideally they should be balanced with some protein. I do not think fruit or veges are needed as part of a before bed snack.
Our go-to snack day and night is peanut butter on a rice cake. It hits the spot without being overly filling. My kids like it with honey. Apple slices dipped in peanut butter are also a favorite of two of my kids. Of course if peanuts are an issue, any other nut or seed butter would do. Good source of protein and most kids like it.
Will he eat cheese with his crackers? Since we were out of peanut butter today (disaster) I made my son a before practice snack of cheddar cheese, crackers and slices of apple and he really loved it.
Does your child like eggs? Maybe you can do some kind of breakfast-for-dinner thing of eggs and toast.
Ok now I'm hungry.