I would cover up most of the egg, but I would leave a gap so I could get the candy/balloon out easily. also 4 the strings, you take yarn and put it in glue. I don't remember if the glue needed 2 B mixed w/ water but, whateves.
My granny used to make these for Easter and she would fill them with treats for me. She would make a little swing out of a pipe cleaner and secure it in place to have a tiny little bunny look like it was swinging inside the egg. I must make these for my girls.