Announcing your engagement at a party is one of the most fun ways to spread the news! You and your fiancé will get the joy of seeing everyone's faces when they learn you are engaged without the awkwardness of asking for gifts. Avoid using social media to invite your engagement party guests and make sure that you don't invite anyone who won't be invited to the wedding.
However, the preferred form of invitation is one that arrives in regular mail with a stamp and street address. Regardless of how casual or formal you go, engagement party etiquette requires that the invitations for the party be mailed 4 to 5 weeks prior to the event and that the invitation wording clearly indicate the date, place and time along with any other important details. Keep in mind that a party is not a requirement nor has it ever been.