Hi Erin,
Other than adding up all the Contact Scores = Account Score, taking a median sounds good. If you want to take into account that two key people are engaged, you can score on that as well. By "engaged" I suspect you mean they are talking to a Salesperson? If so, you could add points based on Status or if sales creates an activity.
But if you mean some leads are doing more behaviors, then you shouldn't worry about this. Your scores should reflect that some folks are engaged and some aren't. So if one person is downloading alot of stuff, and no one else is, then your Account Score should definitely reflect that.
Another way to handle this is to get a predictive scoring service that looks at all account behaviors and past Opp data to make a prediction. Maybe all Accounts with 1 person initially downloading stuff go on to big sales, because that person was tasked with an RFP and is serious about making something happen.