I let them use their hammers to hammer the ice apart. We learned that you can't hammer directly on the toys because it shatters the toys. OOPS! But at least the things that broke were spider rings that they didn't care about.
We also tried to figure out how else we could melt the ice. We discovered that salt helps ice melt but sugar does not. I think we used up the rest of our salt container :)
We also learned that pouring hot water would melt the ice but also spraying the ice with the hose would melt it.
Things we learned regarding this project:
-make sure your tub is freezer safe (mine was not and completely cracked, so now I have no bin)
-don't hammer directly on toys-they will shatter
-freeze ice cubes solidly before adding to the tub (maybe even freeze the tub slightly so the water in there is fairly cool)
-perhaps wear safety goggles while hammering, especially when using the claw side of the hammer