Shall we?

Along with teaching that almost-lovable little monster from my previous post, I've moved right along with my lessons at the middle school. My first day back I decided that after three months with the same group, I should probably learn their names. They've been working on the present-progressive tense so I played the Icebreaker game where you attach an action to the front of your name (i.e. Bouncing Bernadette) and call on people throughout the room. They have a pretty limited range of verbs so the results were pretty interesting. We had a Finding Federico, Taking Tomaso, Noticing Nicola, Voting Valerio, and my favorite: Nursing Natali. I half expected her to lift up her shirt and start "nursing" her pencil bag. Apparently, they teach it as the equivalent to "taking care of". Sure that is part of its definition, but not the first one that comes to mind.
Since most English teachers here in Italy are not native speakers, many things like this go unnoticed. In my roommate's middle school, everyone was taught that "apple" is pronounced "ehpple". Since I found that out, I have been very clear with my classroom on vowel pronunciation.
After the gerund lesson, the teacher of my class showed me the chapter they were working on and what I should focus my lesson on for next time. It was the future tense. But, she pointed out a very specific conversation printed at the front of the chapter in the textbook.
It went like this:

Mary: Hello John.
John: Hello Mary.
Mary: Shall we go to the store?
John: Yes, let's go to the store.
Mary: Shall we invite Susan?
John: Yes! Let's invite Susan.
Mary: Will she meet us there.
John: Yes, she will meet us there. Shall we go?
Mary: Yes, let's go!

The teacher of my classroom: If we could focus on shall for next time that would be great. The kids really have a hard time understanding when to use it.

They have a hard time? I don't think I ever learned it! And I speak English as my first language! Maybe I use it as a joke every once in a while (Shall we stop at the loo? [fake British accent]) but I thought it was considered archaic. In fact, according to Wikipedia, "shall" is considered an archaic term and it is grammatically correct to use will and shall interchangeably in both the US and the UK.
As much as I wanted to go in and blow their tiny little minds with my awesome native language skills, I couldn't exactly go into a lesson and discredit the teacher, their text book and completely confuse the poor kids.
I spent a good hour going over game scenarios in my head, but the thought of little Nursing Natali asking "Shall we buy some tomatoes?" and Voting Valerio responding, "Let's buy tomatoes!" was too hysterical.
I eventually decided to avoid shall all together and make fortune tellers with the class instead. Unfortunately, they're covering the future tense for the next two weeks. What in the world shall I teach them...?