Ah yes, a very good question.

Considering that there will be no verbal communication, I have planned a character to help with this issue.

Floating Text Generator (ftg)

This character does exactly what you think they do; show what they characters are saying.

This will play a big part in dialog!

Why can't they talk? (Story wise)

I can't tell you yet!

Hmmm... that's all for now.

I am dumb and cringe. :]