Enjoyed the story. I would suggest, that to remain credible, all marked death eaters that are students would be rounded up after such an attack and taken by the ministry. Since you had aurors interviewing witnesses, the fact that Draco, at least, was planning to aid the attack would've come out. Only incompetents wouldn't search the rest of the students for dark marks. And since you have a few aurors going with the train, they'll have plenty of time to check each student on the way to Hogsmeade.
As for Harry's whining, Susan and Luna should be able to get him out of that by the time they arrive in Hogsmeade. Although, I imagine that the damage to that village will be bad as well and compound the problem.
Hope you get to writing the sequel soon as it does appear to be 3-4 months overdue.