Though you may well not care, a wedding counts as a public event so you should really seek permission on any modern reading (last 75 years, I think) - Auden, for example, would still be in copyright (it was mentioned on Radio 4 after the popularity of "Stop All the Clocks", used in "4 Weddings & a Funeral"). It may seem petty, but poets don't earn much for their work, so need the royalties. But Shakespeare said plenty on love, and that's long out of copyright!