Class time does not become "time off" for you to grade papers etc. . . . effective management/ facilitation is your "teaching." If that is your view of a project, you're doing this for the wrong reason.
Self-assess along the way and make notes of changes/ tweaks you want for next time.
Don't fear things "going wrong" . . . that's your chance to learn and get it right . . . be flexible on the fly!
Be open to suggestions from students or new proposals.
Don't score a skill that is not part of the objective. Reward students for bein g willing to get out of their "comfort zone."