What is the difference, may I ask? I always thought they were more or less the same thing.
Eyelets only have prongs that bend back to hold it to the fabric, while grommets have a washer that goes on the back and it adds more support to the fabric so it doesnt rip out. grommets are hammered in with a grommet setting set or professional grommet press.
one other thing about using eyelets--
my sister did on a very impressive tie dress thing that she made, and it completely destroyed the strands of fabric/ribbon that she had tried to use to lace up the back...
so I would heavily suggest using grommets instead.
but to each thier own.
ps I forgot to mention BEST WISHES on your big day the first post. =]