DS 6yo has taken a hugge interest in gardening this year. He has a small veggie patch, and we are waiting for the carrots, potatoes and onions and garlic to grow 
I have five or six small terracota and china pots which are sitting round with only weeds growing in them. They are on our north facing patio which actually gets quite a lot of sunlight as the area around our house isn't hugely built up. What can I buy to plant in them which will flower over the summer, and maybe into autumn? Or maybe a mixture of things? Any colours except orange and yellow please. And we already have geraniums and lavender.
As you can tell, I am a complete novice.