Personally, I always consider The Beatles themselves to symbolise in some ways, the excitement and escapism that you see in Child behaviour.
The untouched innoccence of the Psychedelic period is a perfect example of this, as well as the creative style of many of the Beatles projects e.g. Magical Mystery Tour, Sgt Peppers and Yellow Submarine.
John Lennon I would argue, was most intouch with his boyhood nostalgia. In his Own Write and Strawberry Fields (amongst others) show his love and appreciation of where he came from (Liverpool having an obvious link with childhood)
I think without a tad child-like fantasy, The Beatles would not be The Beatles.
I hope that I will (many years from now) still hold on to some of the childhood behaviour that influenced me, as an individual.
Oh, and happy birthday Paul.