Which imaginary friend to choose?

In my quest for a supersim Callisto, her son needs to grow up into an adult and start a family of his own. He is currently still a toddler but will soon become a child. In childhood I want him to befriend one of the female imagenary friends so he can turn her real and eventually marry her. Which one should he choose? The unicorn or crafty kid? Any suggestions for a personality to choose for them, basically anything except evil.

Some background: his mother is Callisto, the granddaughter of a Morgyn Ember clone on her mothers side and a sulani elemental on her fathers side. She is a spellcaster through and through. And a perfectionist as she is doing all apsirations. His father is Kiyoshi, a former mt. Komorebi resident and nowadays a werewolf with a university degree.