I figured it this way.
Giant asleep at top of order, still has condition of unconscious (Thus helpless p.277). Does not wake up on his turn, does not lose conditions.
The 6 of the 10 party members attack variously that round. Although if he takes damage, he still wakes up, conditions are not removed until either the start of the creatures round or the end (p.268-269).
Reading some of the posts, and Re-Looking at CdG outside the game now, I think I did the CDG part wrong. I think they all still made a CdG, because the pre-req's for it still existed, but none could deal the 159HP in one shot to kill it outright.
RAW for 10 1st to 2nd level characters, killing a 13th level Hill Giant would be a good challenge, but I think they could do it. It would not have been a TPK. It might kill 1-2 of them. They all had second winds left, some healing potions, encounter powers, and most healing surges. For fun, we may try the 'what if the giant had not died" scenario and see what happens.
Since this campaign is a fast 'rules learning' campaign, I am leveling them each session regardless of xp. We see character progression, get to use new powers, and experience all levels of play and combat in the new system over 30 weeks then