I think that at the beginning of this lesson we may discuss as a group what "standard punctuation" we would like to include in our protocols. I know this may make the process easier for some but I think the overall planning will be the same regardless of whether we are providing them some hints or not. I am interested in seeing if the students will choose to encode numbers or not.
If they all default to the 1-26 for A-Z (which is exactly what I did), I might challenge them to develop a different one on their own.
A question I have is whether or not people plan to provide some questions or prompts for groups or if you think they should all think of them on their own. There are some of my students who would have no problem doing that, but (as I am sure everyone finds) I have a few that would sit there and say they don't know what to ask.
I like david_ellich's suggestion of having a message on the overhead projector when the students come to class and having them decode it. I may do that as a follow up the next day. I also like tscholtterback's idea of doing a warmup binary puzzle for students to decipher so they are reminded of how binary works. I think this will be a helpful review, especially if I encourage my strugglers to use their Binary Flippy Doo. :0)