radishes-Grow super fast!
lettuce/spinach/arugula-Grow fast and keeps on giving!
zucchini-Will take over the garden
sugar snap peas
strawberry- We haven't grown these from seed, we purchased the plants to transplant from Home Depot and they've been easy to care for.
Container gardening and raised beds are the easiest to grow in. I planted carrot seeds in an old recycling container which turned out to be the perfect depth for the carrots and a good size for my kids-nice and low to the ground. And my plants are doing well in the raised bed compared to directly in the ground-most likely due to poor dirt quality.
Get your kids involved in the garden this year and let them plant their own seeds. It's a quick activity that lasts a season and the kids loved the satisfaction of watching something they planted grow and produce something they can cook/eat.