My 7yo looooooves brussel sprouts. Comments like "a few more pieces of brussel sprouts please mummy" are common in our house.
We also have to donate asparagus to him.
As for cucumber and tomato if you put a plate in front of him he cannot resist. He will keep eating and eating it no matter how much he's had.
You are lucky! In our house, it's really a lot of pb and j, chicken nuggets, white rice, pasta with butter, and oatmeal. That's about it!