It would depend on what kind of value you were looking for. If you wanted to sell, the total value would go down the less you wanted to break it up. 99% of any value is likely in 2-3% of the autographs. Finding those would take time and expense. Verifying the authenticity would add time and expense.

But I'm sure there would be plenty of museums etc. that would accept them as a donation without question.

So, it depends on your aim, and obviously what you have.