Now we do the dance of joy!
It took two weeks for my students to be able to reliably sign into their accounts (blame the fact that school is on a single IP address and I have 100 3-5th graders trying to type lengthy passwords). But now that they can do that without difficulty, things are going brilliantly! They're purchasing real world materials through the system and choosing their engineering project challenges, and almost every student is off doing something different... but with a fair amount of autonomy, so I'm only being driven to the edge of sanity but not over the brink. :) It's so exciting!
Thank you. This resource is so amazingly useful.
http://qlsengineers.online if you're interested in seeing what I'm doing.