I know I'll get a lot of shit now, but what would be so horribly wrong with a blowjob from a cute 7-8 year old? I remember phantazising about sex for the first time myself in that age.
Well you answered it yourself here didn't you.
Phantasising for the first time of a child,
that is something completely different from an adult making his phantasies come true with a child.
A child uttering the first word is not ready to write a story.
A child having the first glimpse of sexual awareness is not ready for sex rightaway.
Maturing takes time.
And for sex maturity is important. Selfesteem. Knowing what you like and what you don't like. Knowing to say no to things and persons you don't want and yes to things and partners you do like. Being mature, having an equal amount of power to begin and end the sexual relation.
And if this is not enough reason for you, seeming to like being in power so much;
Figures tell that kids abused by adults for sexual pleasure are very often maimed psychologically and sexually for life. What is the fun of harming a 7 or 8 year old for life?