I ran the class twice today. Overall it went quite well, and I was surprised at how rapt the students' attention was. I think they really enjoyed trying to guess the meanings of the idioms. I'd say this was one of my more successful lessons.
I did make a couple changes. First, there was a small error on a PPT slide so I fixed that, and I added in some additional graphics to explain the memory game. Second, I added some more animations that I thought made the PPT flow better. Also, I made the worksheet a little shorter, as writing 9 sentences took too long. I will instead have them just write 6 sentences with 6 different idioms (see attached). This also allows me to fit everything on one side of the page.
For the memory game I have decided to use only the 9 idioms that I introduced in the PPT, instead of adding in the extras. I found it made the game a little too hard using additional idioms that I hadn't yet covered. I noticed that when time was up no student groups had come close to matching all of the cards. I think it is challenging enough using the 18 cards, and not 30. So what I did was remove the extra 12 cards from each of the bags.
Finally, if you haven't already printed the cards I'm recommend printing each set on a different background. So you could print different English speaking nations' flags on each set, for example. Having different backgrounds makes it much easier to sort out cards that get mixed up between teams.
The updated materials are attached.