A quick question: let's get acquainted or let's get to know each other?
"Let's get acquainted" is the topic of Unit 1 in a textbook for 12 year old schoolchildren. Is it a usual one? I have thought so because I haven't heard this frase since... well, never, I guess. To me it sounds a bit too formal and I'd like to ask for a native speaker's opinion.
I also wonder, is "let's get to know each other" too colloquial and thus cannot be present in a textbook?