I’m mildly ashamed that I picked this up from Ice Block Day at our local zoo–they freeze toys and food into ice blocks for the animals to play with during the hottest days of summer. Look–if it works for an otter, it works for my twins, okay?
Use a round or square plastic tub, fill it with water, small toys, freezeable treats, etc. Clear a shelf in the freezer and let your appliance do it’s work. The twins cluster around it for hours, howling with triumph as each new goodie melts to the surface.
Seriously, they remind me of Scrat waiting for his acorn to thaw in “Ice Age.”