My parent's are strictly against me having alcohol at the wedding reception, so we will be have a church reception in the afternoon. But my soon to be sister-n-law and father-n-law would still like to have a party for us that same day but in the evening. It will be a very casual party at my in-laws camphouse and they will be grilling for us and our friends. I wanted to just put an insert in with the reception invitation to invite our friends that night. My question is how should I word the "Party" invitation. I want them to know that they're invited to come hang out with us and enjoy a meal and to "BYOB". I just didn't know how to put it in writing and didn't know whether to call it a party or if there was some other word to use.
Sorry, but this is not appropriate or polite. You would be splitting your guests into those who are important enough for a reception with food and those who are not. So, all guests would have to be invited. The one exception is the 'open church wedding' where all of the congregation is invited. Then it is fine to have a church reception, but a small family reception later.
Plus, we never, ever ask our guests to bring the party, especially for a reception and this is what it is. There is no BYOB for receptions. There really shouldn't be for parties either, except when it is strictly family or a group of friends who trade off partying at each other's homes. But, this is still not the best way to host.
As host you or your soon to be family are expected to provide the entire party. So, please only host the party you can afford to host. Perhaps limiting the alcohol to beer and wine would make it affordable.