I invited you to tomorrow's dinner/dinner tomorrow, so you can/could meet my friends

[B45]

I invited you to tomorrow's dinner/dinner tomorrow, so you can/could meet my friends that's all.

Are all four okay to use?

When Should I use can and when should I use could?

 

[MikeNewYork]

All 4 are OK, but there should be a comma after "friends".

There is no easy way to your last question. It depends on context.