None of those are a problem as far as I can tell. And note that the solution is to force string interpolation by prepending ''. to the checkbox_group paramater.
Here's the relevant section of the template:
Please select what additional packages you would like installed via Re
You may select multiple packages. All packages with a check mark wil
+l be installed.
"Even if you are on the right track, you'll get run over if you just sit there." - Will Rogers