I am also in Michigan and had very good lettuce, tomatoes, cucumbers, miniature pumpkins, strawberries last year. I put all of them (except tomatoes) right into the ground, no seedlings. This year I have started Asparagus, but it will take three years until I can harvest (I did not realize it took that long!). We are also trying spinach this year.
About the only thing that didn't get big enough to harvest was the watermelon. I don't think it received enough sun as I put it in the back of the garden with more shade during the day and it took much longer for them to grow to full size. I would start those indoors if I were to do them again this year.