I would give it to the pregnat woman because if she fell she could of hurt the baby and herself and they both could of died. The elderly woman has her stick and could lean back or use her stick to stand up properly. The man with two kids looked like he was holding his two kids comfortably but say he felt uncomfortable he could lean back on something to make it better. I wouln't give it to the man with two crutches because he can stand with it so its not a big problem.
Now there's three seats available the person i think shouldn't sit down is the man with two kids because its only his arms that might be acking and if he sat down his hands will still be acking because he will probably be holding his two kids.