If the kids' space to be physically active is limited, you could have them assemble valentine puzzles.
Cut out one construction-paper heart shape for each child in the class. Cut each heart into random shapes and put it in an envelope for a child to assemble. When a group arrives at the station, give an envelope to each & explain what they are to do.
The 5 or 6 members of each group could compete against each other, or the satisfaction of assembling the heart might be enough.