In 2nd grade we began our talks about the future by reading Someday by Eileen Spinelli. This book is a great springboard into careers because it takes a young girl imagining her future career, then ties it into how what she is doing today is preparing her for each pathway. For example, she is digging in the couch cushions for coins and dreams of being a paleontologist digging for bones.
After the story we played "I Have, Who Has" with careers. I downloaded this game from The Career Day Activity Packet from Teachers Pay Teachers. Each class competed to get the fastest time.
Then I challenged them to come up with as many careers as they could using an Alphabet Chart.
For an extra hint, I played them this video: