Hello, you are probably going to get a lot of different opinions so here's mine.
Take them to the brook and release them into a slow pond area similar to the bucket and they will find a home. Good job taking care of them. I found a bucket similar to what you are explaining while hunting for frogs with my son on my neighbors property. It was full of tadpoles. I went back 2 days later to get them so nothing would happen to them and he had already kicked the bucket over to mow the grass. I can't tell you how much I wanted to..................anyway, good job and thanks for helping them.