Accomodation
Our recommendation would be for you to stay in Agrinio on Friday (for who is coming earlier) and Saturday night.
If you would like to extend your stay after the after-wedding party, our recommendation would be to stay in Messolonghi on Sunday night and spend some time exploring the town, if time permits.
Alternatively, you can return to Agrinio and spend the night there if it is easier for you not to move your stuff. Just bear in mind that you may need to drive back, which is approximately 35-40 minutes.
Here you can find a list of hotel suggestions in Agrinio. You can have a look at those or search for any other hotel or airbnb you prefer :)