my daughter had a hair of hoops that said princess on them and she loved them! have you considered putting a plastic backing and the other backing on the earring? might be harder to fall out that way (my daughter's current earrings she's wearing are put on that way)
look into screw backs they are a tad more expensive because you have to buy them from a jewelery store (so gold earrings) but they do make them in cute styles... my daughter wore little pink elephants for about 2 and a half years and when i took those things out the posts were bent from so much wear and tear but the backings stayed on (i got them at michael hill jewelers)
the backing look something like this (you can get many designs and styles of earring with this style backing)
Attachment 293085