What veggies should I grow ?

Since it's almost August, you'll need to select something that can reach maturity relatively quickly. Lettuce, green beans, snap peas and radishes come to mind. Carrots and beets will continue to mature as the weather grows cooler provided there are an abundance of warm sunny days over the next two months. Time is running short for most other things.

I've never grown cauliflower... so I don't have any idea if they're easy or difficult to grow. When I was growing veggies in pots on my front porch, I grew bell peppers, bunch onions, spinach and lettuce. Bunch onions are really easy to grow. We always bought some from the grocery store, clipped the leaves off to use in cooking and planted the bulb back in the dirt in a pot. As long as you keep watering them during the summer, the leaves would keep growing and you can keep clipping them off to use with eggs or soups. I had to put a wire mesh over the lettuce on our porch because a little fat squirrel thought I'd planted those for him. He'd pull the lettuce up by the roots and eat the whole thing. After I put wire over the top of the pot, he'd sit on it and scold me for blocking him from eating them. (I don't like lettuce but Pretty does.)

@traceyjayne I grow good potatoes (although we don’t really eat potatoes so I give them to our sons) and it’s very easy. I plant first earlies in mid March, 17th usually, and lift them at the end of June. I grow them in potato bags, not in the ground. They like water and they need to be earthed up to keep the tubers away from the light. Courgettes are also easy.

I grow corn, green beans and sunflowers in the Summer.

I don't really have much idea about what would grow well there. Good luck with whatever you decide.