My fiance and I are eloping, dish to pass, bad taste, improper or no?

We decided to get a justice of the peace and have a little casual thing on the beach, neither one of us want a big wedding, we want something that is personal, just us. Budget is a bit tight so we are going to have the "reception" in a park, nice family gathering. Is it considered bad taste or improper to ask guest to bring a dish to pass? Its kind of an open invite thing, if you come you come, if you don't well then you don't