Could the purple flower be zinnias? They are very easy to grow.
I think it's great that you are wanting to plant something IRL (in real life). Green beans are great for kids as they grow really fast and they can pick the beans right off the plant to eat. My LO and her cousin love grazing in our garden which has sweet peas, green beans, mint, basil, dill, spinach, tomatoes, potatoes, cilantro, and watermelon. I think they enjoy the novelty of growing something and being able to eat it more so than buying it at the store.. especially beans and the grape/cherry tomatoes! Ha ha - my daughter loves to eat the dill right off the plant rather than picking a piece off. It's amazing how easier it is to get her to eat veggies when she can see them grow =)
Good Luck with which ever plant you decide to grow!