I done something similar. If you can afford a GoPro go ahead that'll be a much better option. During my De-brief's with the instructor I used the voice recorder on my iPhone to play back the de-brief later on once I was out of the excitement that I had just been flying. I found that I was more likely to improve for the next lesson having listened to what hints and tips the instructor gave.
Good luck for the lessons, best and most well spent 47hrs of my life!