Honestly, making homemade marshmallow squares cut out of a pan is a lot easier than making marshmallow eggs poured into a mold, but if your children, like mine, are super-excited about making eggs, here's your warning that it will be messy.
Also be warned that these are insanely good. Your children will thank you! Your hips will not.
I'm going to be lazy for recipes I didn't create-- too lazy to even cut and paste. I found the recipe here. Go forth and marshmallow!