Update - tried the game for 2 lessons this morning, and the kids really enjoyed it.

You might want to add a few more 'high scoring' letters though, as some teams were a bit stuffed when they only had a bunch of 1 point letters. Or perhaps give them the opportunity to change some letters at various stages during the game.

Also smaller teams would probably work better. I had my classes of ~28 students split into 3 teams, so quite a few Ss per group. Maybe groups of 5-6, but with 8 letters each, would work better.

Hope this helps!