Agree with your feelings about children?s bangles etc. I have several from my childhood and never wore any of them - stuffed in a drawer taking up space and with little sentimental value as they were never worn and are too small now etc. etc. The little cards that my mum kept for me with well wishes to me written by the distant rels. that sent them are more important to me...
Two ideas we have done for our little one - I bought a lovely leather bound book when she was born, stuck in a photo and wrote her a letter (drafted out carefully elsewhere first) and then have added another picture with a letter on her 1st and 2nd birthdays talking all about my changing worries, hopes and fears for her, how much I love her, highlights of the year, her achievements etc. Will have to see if I hand it over on her 18th, 21st or maybe if she has children herself on the birth of the the first one - got time to think about that one! Hopefully she will value it as much as I hope she will. Certainly more personal between us than a piece of jewellry bought quickly on a Sat. morning - but that is just my opinion (based on my dislike for jewellry more than anything ).
Another thing we are doing is collecting the No.1 hit on each birthday ready for her 18th party...My dh?s parents did this for him (not Cds of course!) and it still means a lot to him.
Good luck deciding what to do.