Ok, you play as a sexually voracious female pedo who is into little boys, the younger they are and the smaller their prick sizes the better they are for her tastes (her ultimate favorite might even be a premature newborn with a microcock).
The story starts with you making your character and her being born, starting with you as a newborn and follows her throughout her entire life as you are guiding her into seducing and having her way with the various young boys she encounters, including her own family members (like her brothers, nephews, and cousins).
Along the way you earn points for everything you do with each of your conquests, which you could use to improve your character as she screws her targets, and these points are used RPG style to improve your character in various ways, each of which will help you to fuck some young kid that you are after (usually from a matching archetype to the stat being improved: getting fit will help you get the kid athlete, getting smart will help you get that kid genius, etc).
How you can go about it is getting into various positions that aid you in your encounters and endeavors, such as becoming a babysitter, teacher, coach, salesclerk, servant, prostitute/pornstar, etc.
Many jobs which earn you money that you could use to help you in your quest.
You need to avoid getting caught, as that would lead to prison and a game over, which means that you need to navigate the gauntlet that gives you access to your target, and then you need to be careful in your approach with them in order to avoid getting caught.
Yes, a "grooming sim" is a far more apt description of this idea than a "dating sim".
Your tutorial begins with you as a baby yourself, and from there you are guided through the basics and have your first experience with a loli-shota pairing between you and your twin brother.
All the boys have dicks shorter than 6 cm, and on average they have dicks around 4 cm in length, the source of your power comes from the pleasure you provide to them, the younger they are and smaller their peens are, the more points you gain from pleasuring them, but also they are harder to have sex with (both in getting into doing the deed, in the actual sex itself, and in getting away with doing it).
This will be a guide for grooming the way GTA is a guide for car theft, we will also place a disclaimer at the start that says that this is a work of fiction in which all characters are over 18 and consenting, before making the game explicitly state the ages of the targets as being in the single digits, and depict them as such (a joke at how meaningless such disclaimers are when it comes to pornographic works with wholly fictional characters and events).
Yeah, I know, but we needed some sort of loss condition to make the game a game.
Does this idea fit into your description?