Then I think you have a problem...
Then again..... you could also buy a large bucket/container/storage box in plastic and do the same thing. Your cost could either be shared withthe others or look at it as an investment should you ever decide to do it again.
Leave it frozen til the day before you have a couple of days off. If it is that big you should not have any worries for 12 hours or so. The coldness will keep the water chilled plenty at the beginning and I seriously doubt you will have any issues. (unless your temperatures at the moment are into the 90's - then think of it as a bonus for cooling the house.)
Last but not least, cover a room in plastic drop sheets and get out the chainsaw!
Next time I bet you'll think twice before a sweet deal like that.
Good Luck and let us know what happens!