To add to what the others have said, I would keep the ground very moist/wet where the slab is going. That should help ****** "wicking" from the crete into the ground, slowing the drying.
I've done this lots of times before I retired. You've been given some good advice about the temperature and keeping the ground wet. Two able bodied men will not have any trouble, but a third would make light work of it. I've done over 50 bags with two men, but you know you've been working when it's finished. There will be no coffee breaks with two workers.
Thanks for the replies. I do have bucket on the tractor but can not get it in to where this concrete is going. I will look into the U-cart type deal or wait until it cools down some.
Maybe renting a larger mixer that can hold 2 or more bags would make the job easier, or use your small mixer and a larger rental , that :drink:would really make the project go!