I like the name. I rarely see or interact with children, so
Allison /
Alison would not seem "dated" to me in any way; I know or have known quite a few ladies of my own approximate age by this name.
Some will like or prefer to call
Alison -
Alice or other variation, while some may dislike Alice--etc, so doubling the letter "l" could also be to dissuade the use of these variants - we have "
Allie"?; some however may just prefer to see the two letters.