Traditionally, the bride's parents are responsible for hosting and paying for the engagement party. However, this tradition is no longer locked in place, and the party may be hosted by the newly engaged couple or any combination of family and friends.
Engagement parties should be scheduled no later than three months after the engagement is announced. According to About.com Etiquette, the guest list should include immediate family, close extended family, and the bride and groom's intimate circle of friends. Invitations may be sent via regular mail or e-mail. Gifts are usually not expected at an engagement party, and the invitation should make that very clear. Overall, an engagement party is intended to be a light and happy event that celebrates the bride and groom. It should not be used as an opportunity to discuss wedding details, make guest lists or choose the bridal party.
TheKnot.com states that engagement parties traditionally were designed to help the bride and groom combine and introduce their families. However, if the engagement party is the first time that the parents of the bride and groom are meeting, it is best to provide them with a private place to do so. This allows them time to get to know each other without the interference of others.