What is the Sunnah ceremony when opening a new Musjid?

Answer

There is no Masnoon opening ceremony for a Musjid. People simply enter to perform Salaat. The ceremony described by you and the ceremonies generally practised for opening Musjids are all bid'ah. There is no basis in the Deen for such khuraafaat (nonsense). These are all bid'ah merrymaking programmes of ujub, riya and takabbur. Opening ceremonies are in emulation of the kuffaar.