You should wear casual attire when you meet your boyfriends family for the first time.
Semi-formal means dress clothes. Girls should wear dresses and heals, men should wear suits.
They're formal events, and that's the attire you should wear.
Wear what ever u want!
A Tux
Sperry's?
No.
nothing
bikini
A Tux is generally suitable for semi formal evening events like prom, wedding parties, charity events, award ceremonies. For more formal events, you should wear suits.
If it is formal, that will be fine. If it isnt formal, I would just suggest a shirt.
Something nice, semi-formal and comfortable.