You shouldn't need to buy anything different.
At his age he can eat mostly anything you do, as long as it's not salty, sugary or too low fat. Also best to avoid honey and nuts.
At that age mine were eating for breakfast things like cornflakes, rice crispies, Weetabix, shreddies, porridge, toast fingers, scrambled egg, fruit, yoghurt.
Lunch would be sandwiches (ham, chicken, cheese, cream cheese, egg mayo, tuna, Marmite), chopped fruit, cheese chunks, breadsticks, beans on toast, scrambled egg (if not had for breakfast), tomatoes, carrot sticks, cucumber, things like that.
Dinner would be whatever we were having - shepherd's pie, roast with potatoes and veg, spag bol, pasta dishes, curry, chilli (not too hot!), jacket potatoes with quiche and salad, most things really.
We don't really do puddings but offer yoghurts, fruit, rice pudding.
Hope that helps.