I understand you want ideas not opinions. But 80 presents has to be something that person would like. You know them much better than we do, but you have not given any clue as to what presents you have thought of so far.
I can only presume you haven't thought of many, hence the ask for help. But that also probably means it is difficult to think of 80 presents anyone would like.
How many other 80 year olds do you know, and have you asked them what they think of this idea? I know/have known approximately 20 people (well) who have been or are shortly to be 80, and none of them would have liked this. Have you ever seen anyone open that many presents? Or even a quarter of that number? All from one or two people? How many other people are in your family? Who else will be there when she opens these presents? A nice present should take at least 2 minutes to open - admire the wrapping, open slowly, express pleasure, thank the giver, talk about it a bit. 80 of those, with slight elongation for some, is 3 hours straight!!!!
You seem certain it is a good idea, but you have not responded with reasons why, or acknowledged the points made. If would understand better if you had said 'I know it is a lot, my ideas so far were.... and this is how it won't be overwhelming'.
Still, since you have asked, as well as loving the memories idea, I would suggest themes eg:
Either 10 seeds, 10 chocolates, 10 biscuuits etc (I have soon run out of ideas!) or
10 things from each decade of her life (personally I think that is too many - 1 from each decade would be plenty).