They should be fine, for a short period. A pool is a lot larger than the peanut pond and RubberMaid tubs I had my fish in when I enlarged my pond this past spring, and all mine came through great.
Be sure to fill the pool with the same water you take out of the pond, at the same time, so the temperatures are equal. Depending on how many fish you have and how long they will be in the pool, they will use up oxygen quickly, so put in lots of submerged plants. Get a pump set up to create a splash, to add oxygen to the water. I also had pumps with air stones, like you use on indoor aquariums, to aereate the water. I asked for some on my local chapter of FreeCycle.com and someone gave me three.
And be SURE you put a cover on the pool. Screen, lattice, boards, whatever. The fish will be unhappy, and you can bet they will jump out if they can.