One question answered, Arthur is Head Boy so Molly is a 7th yr also. Well maybe not depending on your timetable. I like that Arthur has siblings in your story.
Interesting the Marauder's pulled their first prank without even knowing they were doing it. Dentention first day of school. Bet James and Sirius set a new record there.
New take on what Remus tells his friends at first. Because there was never any info on the background of Remus or Peter, it's interesting to see what writer's come up with.
I'm still liking the story.