I strongly prefer Teams in the morning for melty to get people to loosen up, than do singles afterwards to finish grand finals into the night. If WB is any learning experience, everyone is DEAD for teams after singles. Overall I don't really think it matters, though. If we have time on the floor to run both, it'll be better.
Teams, being single Elim, shouldn't take more than 2 hours. If a solid 12 hours is set aside for melty, like 11am-11pm it'll run pretty smooth. As far as I know Melty was supposed to start around like 3pm though? How's the schedule look, it could be tough to run teams after singles. Like you said though, if signups are done during singles, it shouldn't be a problem.
Having a megaphone, really, really, really helps.