I don't find any problem with your sentence.
Student or Learner
I have just read that we cannot use "would"/"used to" for repeated events in the past if we mention how many times in total something happened.
Does it mean that the following sentence is wrong?
"When I was a child my Dad would take me to the cinema 3 times a week."
If I used "used to" in this sentence instead of "would", would it still be correct?
When I was a child my Dad used to take me to the cinema 3 times a week
I think you misunderstood the "rule" that you quoted. The phrase "three times a week" is a frequency, not a total number.
If your father took you to the cinema a total of three times, you would not use "would" or "used to".