Thanks for the input, and maybe "skills" challenge wasn't the right title!
This is the second annual retreat with most of the same sewers coming back. The individuals vary in their interactions during sewing times - some wander and look, some sit and sew, other pair up with a friend, but all are very friendly and sociable. In the evening we had a couple games, mostly to help all of us get to know each other if we weren't acquainted already. It was a very successful retreat with everyone wanting a repeat this year.
The first time our activities were 1- we had a pen/paper type of activity and 2 - a 2 1/2 inch strip activity.
I've been nominated to organize the games this go round and due to popular requests, the strip activity will be repeated. I have a pen/paper type of activity planned and had thought a small sewing based activity would be fun. I didn't want anything that would take more than a few minutes, recognizing most if not all of us are there to sew!
What I think we'll do is an activity based on a log cabin that I've brainstormed with a friend - not overly time consuming, not overly competitive and winner can choose to take the finished squares or donate to a group that does charity quilts. Thoughts?