For decoupling, not sure what's best. 100 nF is very common for digital chips. I have seen 10 nF as well, and for another project I'm using a 1 µF ceramic + 22 µF electrolytic on a 555. In some cases you even see multiple decoupling cap: 0.01, 0.1 and 1 µF ceramic and a larger (10-47 µF) electrolytic. This to catch more frequencies. Each cap is most effective at certain frequencies.
As you see, the values are not critical, and this is one of those points where art and engineering overlap.