It turns out that two bicycle gift bags will work. Tell me this doesn't look like a giant headless matron in an evening gown. A masterful deception I think.
Our Christmas was delayed a few days until one family member was back home, which gave me some extra time to work on the project. I didn't quite get everything done, but enough that I could assemble it and have it ready for the celebration. I'm happy to say it was a big hit. In the next week I'll tie-up the loose ends and get it re-assembled in the family room. For now, here are a few photos of the substantially complete structure.