1. According to the basic halacha, it is permissible to eat the Purim feast in the morning, but the custom is not to because in the morning people are occupied in sending Mishloach Manosup until the time to pray Minchah, and once that time comes, it is forbidden to eat before praying Minchah (Shulchan Aruch and Mishnah Berurah 695).
2. On Purim one should pray Minchah as early in the day as possible. The feast should then be held such that most of it will take place during the day rather than beginning it close to nightfall and then eating most of it after Purim! [When Purim falls on a Friday, the meal should be eaten in the morning in honor of the Shabbos] (ibid.).
