How to announce the housewarming in the group?

In this case, you can write an invitation.

According to the industry encyclopedia, the name or title of the invited person is written on the cover, such as: presented to Mr./Ms. XXX. The text is written on * * * days in the solar calendar and * * days in the lunar calendar. For the housewarming banquet, we will wait for you in the banquet hall on the first floor of XXX Hotel. The name of the host, the name of the hostess. Make an appointment (time) and wait (time) to be seated.