Just used this lesson in class, and it went over pretty well!

I think the last activity can be a bit difficult in a loud class with a few extra quiet speakers. It was successful as a group activity in my smaller girls classes, but was more difficult with the large class of all boys!
I think Activity #3 can also be done together as a whole class.
The way I did this for the big classes was assign columns of students 1 of the 5 groups of words. Then the first row of students played the game. The first person to make a mistake would be finished, and then we'd begin again with the person behind them taking over their place. The team with the most students left when one team reaches 0 players would be the winner.
Alternatively, you could just play it in rows of students, and at a mistake the team gets a minus point, and then the next row of students behind them would begin the game again.
Also, in activity #2, some funnier sentences work well, especially if you let them chose. My students liked:
1. What are you doing?
2. I think you are crazy.
3. That was so fantastic.
4. Tell me what you know.
It's also beneficial to go over what a "syllable" is, demonstrating in both Korean and English. It's pretty easy to see syllables in Korean, and once you give them the hint of vowel sounds (A, E, I, O, U, and sometimes Y), it pretty easy to pick up in English. Just as long as they don't only count vowels, but the sounds they make.
For example:
favourite has 5 vowels, but only 3 syllables.
Anyways, great lesson idea! Thanks for uploading it.