I like
Wendy. It's been around a while but it doesn't sound dated. I can easily see it on someone old ('Aunt
Wendy' sounds very natural), or a little kid or a teenager or pretty much any age.
I think of
Peter Pan, not the fast food restaurant.
It fits with a wide range of middle names too. It sounds nice with 'boring' middle names and some longer fun ones:
Wendy Rose Wendy RosalineWendy Emilia Wendy Hannah Wendy Marie Wendy CarminaWendy Lucretia Wendy Amelia Wendy AdelaideWendy Victoria Wendy ViolaWendy Jane Wendy Florence Wendy DorotheaWendy JenniferWendy AmaliaWendy Adele Wendy Adeline