Salamu alaykum
I dont see a point in this. He is risking his family being attacked for doing this. Especially, having his daughers or wives with him and bending over and prostraying down while other man are starring at them. There should be hayyah (modesty) jealousy of his family. Also, it's not like they were walking and suddenly decided to pray. Since they had a guy recording or maybe it was not someone with,them, but it this seems like they were trying to mock them (by praying by the former mosque)or be sarcastic. Person should do dawah in the best way with sencirity wanting the people to accept islam as Allah says in quran and to call with hikmah. I believe most of the time Muslims miss use their freedom in western countries and then become arrogant. Actions like this will lead to more restrctions.
Allah knows best
Wassalam