I recommend verifying that with a CM prior to your HS day. A simple phone call to the tech support line or to guest services and they'll adjust your list in MDE ahead of time. You'll have a far less stressful experience if it's ready ahead of time. That way, you can confidently ignore the checklist of people in your party when you're in the park trying to click "join" and get that BG. As long as they've tapped the magic band or ticket to get into the park that morning, and they're on your list in MDE, then there's no issue with them being included in your BG when you get one.
IMHO